主题：如何判断excel数据表不存在

Dim g As String = "d:\date\"
Dim r As String = e.Form.Controls("TextBox1").Value
Dim rr As String = ".xls"
Dim mg As New Merger
mg.SourcePath = "" & g &  r & rr & ""
mg.Format = "excel"
mg.SourceTableName = "订单$"
mg.DataTableName = "订单"
mg.Merge()

用以上合并数据代码，只要excel数据表的名称输错，即跳出一长串的错误信息。请教，如何用代码判断excel数据表不存在。