A megoldás amit kerestél:

Sub MessageBoxTimer()
Dim AckTime As Integer, InfoBox As Object
Set InfoBox = CreateObject("WScript.Shell")
'Set the message box to close after 10 seconds
AckTime = 10
Select Case InfoBox.Popup("Click OK (this window closes automatically after 10 seconds).", _
AckTime, "This is your Message Box", 0)
Case 1, -1
Exit Sub
End Select
End Sub