Modifying the UDF to Handle Array of Cells

Oct 13, 2025 by wbrum.org 86 views

Introduction

In Excel, User Defined Functions (UDFs) are a powerful tool for automating tasks and creating custom formulas. However, when writing UDFs, it's essential to consider how they will handle different input scenarios, such as being passed a single cell or an array of cells. In this article, we'll explore how to write Excel UDFs that can handle both single cell and array of cells inputs.

Background

I wrote the below UDF to check whether a cell's contents is valid (i.e., if a cell's data validation is set to a list of A, B, C. Returns TRUE if the cell is "A", "B", or "C", and FALSE otherwise).

Function IsValidCell(cell As Range) As Boolean
    IsValidCell = cell.Validation.Formula1 = "A,B,C"
End Function

However, this UDF only works when passed a single cell. If you pass an array of cells, the function will return an error. To make this UDF more robust, we need to modify it to handle both single cell and array of cells inputs.

Modifying the UDF to Handle Array of Cells

To modify the UDF to handle an array of cells, we need to use the Application.Transpose function to convert the array of cells into a single array. We can then use the Application.Match function to check if the value in each cell is in the list of valid values.

Function IsValidCell(cell As Range) As Boolean
    Dim arr As Variant
    arr = Application.Transpose(cell.Value)
    Dim i As Long
    For i = LBound(arr) To UBound(arr)
        If IsError(Application.Match(arr(i), Array("A", "B", "C"), 0)) Then
            IsValidCell = False
            Exit Function
        End If
    Next i
    IsValidCell = True
End Function

However, this modified UDF still has a limitation. It only checks if the value in each cell is in the list of valid values. It doesn't check if the value is actually a valid value for the cell's data validation. To fix this, we need to use the Application.WorksheetFunction object to get the list of valid values from the cell's data validation.

Function IsValidCell(cell As Range) As Boolean
    Dim arr As Variant
    arr = Application.Transpose(cell.Value)
    Dim i As Long
    Dim validValues As Variant
    validValues = Application.WorksheetFunction.Transpose(cell.Validation.Formula1)
    For i = LBound(arr) To UBound(arr)
        If IsError(Application.Match(arr(i), validValues, 0)) Then
            IsValidCell = False
            Exit Function
        End If
    Next i
    IsValidCell = True
End Function

Using the `Application.Union` Function to Handle Single Cell and Array of Cells

However, the above modified UDF still has a limitation. It only works when the input is an array of cells. If the input is a single cell, the function will return an error. To fix this, we need to use the Application.Union function to handle both single cell and array of cells inputs.

Function IsValidCell(cell As Range) As Boolean
    Dim arr As Variant
    If cell.Count > 1 Then
        arr = Application.Transpose(cell.Value)
    Else
        arr = Application.Transpose(Array(cell.Value))
    End If
    Dim i As Long
    Dim validValues As Variant
    validValues = Application.WorksheetFunction.Transpose(cell.Validation.Formula1)
    For i = LBound(arr) To UBound(arr)
        If IsError(Application.Match(arr(i), validValues, 0)) Then
            IsValidCell = False
            Exit Function
        End If
    Next i
    IsValidCell = True
End Function

Conclusion

In this article, we've explored how to write Excel UDFs that can handle both single cell and array of cells inputs. We've modified the original UDF to use the Application.Transpose function to convert the array of cells into a single array, and the Application.Match function to check if the value in each cell is in the list of valid values. We've also used the Application.WorksheetFunction object to get the list of valid values from the cell's data validation. Finally, we've used the Application.Union function to handle both single cell and array of cells inputs. With these modifications, the UDF is now more robust and can handle a wide range of input scenarios.

Example Use Cases

Here are some example use cases for the modified UDF:

You have a range of cells that contain data validation, and you want to check if each cell's value is valid.
You have an array of cells that contain data validation, and you want to check if each cell's value is valid.
You have a single cell that contains data validation, and you want to check if the cell's value is valid.

Best Practices

Here are some best practices to keep in mind when writing Excel UDFs:

Use the Application.Transpose function to convert arrays of cells into single arrays.
Use the Application.Match function to check if values are in lists of valid values.
Use the Application.WorksheetFunction object to get lists of valid values from cell's data validation.
Use the Application.Union function to handle both single cell and array of cells inputs.

Q: What is the difference between a single cell and an array of cells in Excel?

A: In Excel, a single cell is a single cell that contains a value, while an array of cells is a range of cells that contain multiple values.

Q: Why is it important to handle both single cell and array of cells inputs in Excel UDFs?

A: It's essential to handle both single cell and array of cells inputs in Excel UDFs because it allows the UDF to be more flexible and robust. If a UDF only handles single cell inputs, it will return an error when passed an array of cells, and vice versa.

Q: How can I modify an existing Excel UDF to handle both single cell and array of cells inputs?

A: To modify an existing Excel UDF to handle both single cell and array of cells inputs, you can use the Application.Transpose function to convert the array of cells into a single array, and then use the Application.Match function to check if the value in each cell is in the list of valid values.

Q: What is the `Application.Transpose` function, and how does it work?

A: The Application.Transpose function is a built-in Excel function that converts a range of cells into a single array. It takes a range of cells as input and returns a single array that contains the values from the range.

Q: What is the `Application.Match` function, and how does it work?

A: The Application.Match function is a built-in Excel function that searches for a value in a list of values and returns the position of the value in the list. It takes a value and a list of values as input and returns the position of the value in the list.

Q: How can I use the `Application.WorksheetFunction` object to get the list of valid values from a cell's data validation?

A: To use the Application.WorksheetFunction object to get the list of valid values from a cell's data validation, you can use the Application.WorksheetFunction.Transpose function to get the list of valid values from the cell's data validation formula.

Q: What is the `Application.Union` function, and how does it work?

A: The Application.Union function is a built-in Excel function that combines multiple ranges of cells into a single range. It takes multiple ranges of cells as input and returns a single range that contains all the cells from the input ranges.

Q: How can I use the `Application.Union` function to handle both single cell and array of cells inputs?

A: To use the Application.Union function to handle both single cell and array of cells inputs, you can use the Application.Union function to combine the single cell and the array of cells into a single range, and then use the Application.Transpose function to convert the range into a single array.

Q: What are some best practices for writing Excel UDFs that handle both single cell and array of cells inputs?

A: Some best practices for writing Excel UDFs that handle both single cell and array of cells inputs include:

Using the Application.Transpose function to convert arrays of cells into single arrays.
Using the Application.Match function to check if values are in lists of valid values.
Using the Application.WorksheetFunction object to get lists of valid values from cell's data validation.
Using the Application.Union function to handle both single cell and array of cells inputs.

By following these best practices and using the modified UDF, you can create more robust and flexible Excel UDFs that can handle a wide range of input scenarios.

Conclusion

In this Q&A article, we've explored some common questions and answers related to Excel UDFs that handle both single cell and array of cells inputs. We've discussed the importance of handling both single cell and array of cells inputs, and provided some best practices for writing Excel UDFs that handle both input scenarios. By following these best practices and using the modified UDF, you can create more robust and flexible Excel UDFs that can handle a wide range of input scenarios.