Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        Dim iSection As Integer
        Dim iTries As Integer
        Dim oExcel As Object

        ' Enable an error handler for this procedure.
        On Error GoTo ErrorHandler

        ' Start Excel, giving it focus.
        Shell("C:\Program Files\Microsoft Office\Office10\Excel.exe", _
            AppWinStyle.MinimizedFocus)

        ' Move focus back to this form. (This ensures the Office
        '  application registers itself in the ROT, allowing
        '  GetObject to find it.)
        AppActivate(Title:=Me.Text)

        ' Attempt to use GetObject to reference the running
        '  Office application.
        iSection = 1 'attempting GetObject...
        oExcel = GetObject(, "Excel.Application")
        iSection = 0 'resume normal error handling

        ' Automate Excel.
        oExcel.ActiveCell.Value = "Hi"
        MsgBox(oExcel.Name & ": able to GetObject after " & _
            iTries + 1 & " tries.", MsgBoxStyle.MsgBoxSetForeground)
        
        ' You are finished with automation, so release your reference.
        oExcel = Nothing

        ' Exit procedure.
        Exit Sub

ErrorHandler:
        If iSection = 1 Then 'GetObject may have failed because the
            'Shell function is asynchronous; enough time has not elapsed
            'for GetObject to find the running Office application. Wait
            '1/2 seconds and retry the GetObject. If you try 20 times
            'and GetObject still fails, assume some other reason
            'for GetObject failing and exit the procedure.
            iTries = iTries + 1
            If iTries < 20 Then
                System.Threading.Thread.Sleep(500) ' wait 1/2 seconds
                AppActivate(Title:=Me.Text)
                Resume 'resume code at the GetObject line
            Else
                MsgBox("GetObject still failing. Process ended.", _
                    MsgBoxStyle.MsgBoxSetForeground)
            End If
        Else 'iSection = 0 so use normal error handling:
            MsgBox(Err.Description, _
                MsgBoxStyle.MsgBoxSetForeground)
        End If
    End Sub