将以下代码 插入主窗口的代码中：

Private Sub Form_Load()
Call CheckExist(Me)
End Sub
Public Sub CheckExist(fm As Form)
Dim title As String

If App.PrevInstance Then
title = App.title

Call MsgBox("这程式已执行", vbCritical)

App.title = "" '如此才不会Avtivate到自己

fm.Caption = ""
AppActivate title 'activate先前就已行的程式
End
End If
End Sub