Report Builder - how to capture errors when using VBA macros to refresh data

Hello all,

I have an Excel 2013 workbook that has two Report Builder requests.  Request B (a Page Path report) is dependent on Request A.  Request A references data entered by the user.  If the user enters bad data (a non-existent URL path) then Request A returns no data and Request B fails with "Pathing patter filter cannot be empty".

I am trying to give the user a more friendly error, since I know what most likely caused the error, i.e. the aforementioned bad URL string.  I have added error handling just to see what I can get, but the code is apparently ignored.

On Error GoTo ErrorHandler

....

Exit Sub
ErrorHandler:
    MsgBox ("Error number: " & Str(Err.Number) & vbNewLine & _
           "Source: " & Err.Source & vbNewLine & _
           "Description: " & Err.Description)
End Sub

Any ideas of how to capture and overwrite the built in error message?

Thanks,

Kathryn