Macro doesn't work with another workbook acitive

The macro below runs fine until another workbook is the active workbook. What can I do to change this macro to make it work while I have another workbook open and active. The macro works fine as long as the workbook to which it belongs is the active workbook. It will halt on the line beginning with Set rnAR_Dest with an Error 9 Subscript out of range.

Private Sub ActivateRange()

    stAR_ConfigSheetName = "arConfig_" & Me.Name
    Set rnAR_Dest = Me.Range(Worksheets(stAR_ConfigSheetName).[ar_range].Value)
    Set rnAR_Table = rnAR_Dest.Resize(1, 1).Offset(1, 1)
    Worksheets(stAR_ConfigSheetName).[ar_YFAttributes] = GetCurrentYahooFinancialAttributeTags
    
End Sub