关于VB开打word文件的错误处理

关于VB开打word文件的异常处理
Dim ofd As New OpenFileDialog()
  ofd.Filter = "Word Files(*.doc/*.docx)|*.doc*"
  ofd.ShowDialog()
  Dim oWord As Word.Application
  Dim oDoc As Word.Document
  Dim oDlg As Word.Dialog
  Dim oSel As Word.Selection
  oWord = New Word.Application
  oDoc = oWord.Documents.Add(ofd.FileName)
  oDlg = oWord.Application.Dialogs(Microsoft.Office.Interop.Word.WdWordDialog.wdDialogDocumentStatistics)
  oSel = oWord.Selection
我是用VB打开某个word文件然后检查里面的的格式
点击按钮以后会弹出选择文件的dlg
这时如果点取消不选择文件则会继续后面的检查
如何判断是否有文件被打开?

[解决办法]
顶一下先，顺便学习