You might check if the worksheet name exists before trying to add it.
Function Test_WorkSheetExists()
MsgBox "WorksheetExists? " & WorkSheetExists("Sheet1"), _
vbInformation, "ActiveWorkbook.ActiveSheet"
End Function
'WorkSheetExists in a workbook:
Function WorkSheetExists(sWorkSheet As String, Optional sWorkbook As String = "") As Boolean
Dim ws As Worksheet, wb As Workbook
On Error GoTo notExists
If sWorkbook = "" Then
Set wb = ActiveWorkbook
Else
Set wb = Workbooks(sWorkbook)
End If
Set ws = wb.Worksheets(sWorkSheet)
WorkSheetExists = True
Exit Function
notExists:
WorkSheetExists = False
End Function