Excel error 1004 "Unable to get .... property of WorksheetFunction class" appearing inconsistently

Question

I have a VBA function within a spreadsheet which operates on another spreadsheet that is opened in an earlier stage of my macro. The macro used to work fine but just recently has started causing a 1004 error ("Unable to get RoundDown property of the WorksheetFunction class") when it runs.

I believe I understand what the error would be caused by (a problem running RoundDown) but I cannot see why it is getting triggered in my macro and the odd part is that when I go into Debug mode and step through the code in the VBE the error does not recur (despite nothing obviously changing).

Does anyone have a similar experience of this sort of error occuring inconsistently and know what I could do to resolve it?

I'm reasonably VBA/Excel-savvy, but any suggestions on further steps to diagnose it would be appreciated. I am wondering if there is some issue with the opened spreadsheet not being ready but I cannot see how.

The code is here. The error occurs on the line marked with a comment.

Public Function GetDatesA(sWorkbookname As String, sSheetname As String, sCell As String) As Variant

    Dim vDateList() As Variant
    Dim currentCell As Range
    Dim n As Long

    Set currentCell = Workbooks(sWorkbookname).Worksheets(sSheetname).Range(sCell)

    n = 0

    Do
        If Trim(currentCell.Value) = "" Then
            Exit Do
        Else
            ReDim Preserve vDateList(0 To 1, 0 To n)
            vDateList(0, n) = WorksheetFunction.RoundDown(currentCell.Value, 0) 'error occcurs on this line
            vDateList(1, n) = currentCell.Column
            'Debug.Print currentCell.Value
        End If
        Set currentCell = currentCell.Offset(0, 1)
        n = n + 1
    Loop While currentCell.Column < XL_LAST_COLUMN

    GetDatesA = vDateList

End Function

Other details are:

• Excel version: 2010

• File being opened resides locally on my C: drive; my macro is in a spreadsheet on the network

• File format for both files is .xls (i.e. Excel 2003) - I don't have the option of changing this

• Windows 7 (not that I think it would be relevant)

Two points I've tried already are:

• Substitute a different worksheet function (e.g. Min(currentCell)) and that also causes the same problem

• Having the file open already seems to stop the problem - I wonder if there is some way that the workbook which is being opened (rather than my main workbook with the macro in it) is not enabled for macros and this is interfering. But even if this is the cause I'm not sure how to get around it!

Any ideas?

Answer 1

This error occurs often when any argument passed to the worksheet function is not of the correct type or simply doesn't make sense.

For example, I've had this problem when calling WorksheetFunction.Asin with an argument bigger than 1. In your case, I'd guess currentCell.Value is a non-numeric value or one not according to your region settings regarding numbers.

Yes, the error message is really misguiding.