事件回滚问题哪位大虾帮忙？？？？

[surpriseruck]

我运用了事件回滚，但一直报错，请帮我看一下
Public Function ExecSql(ByVal SqlStr As String) '添加、删除、修改
On Error GoTo Err_Rollback
Set cnn = New ADODB.Connection
' cnn.BeginTrans
cnn.Open ConnectString
cnn.Execute SqlStr
' cnn.CommitTrans
Set cnn = Nothing
Exit Function
Err_Rollback:
' cnn.RollbackTrans
Resume Err_Rollback
End Function