OK just for info, Yes you can do it, here is a test Sub to show you how:
Note: This does not use the Excel MsgBox, it uses the Windows Scripting MsgBox which looks the same but works differently. This box allows a auto responce where the Excel MsgBox does not [Yes and No there is a nasty Class code to do it, but it is real limited.] This Script MsgBox works great and it is easy!
Sub myTimeBox()
'Sheet module code, like: Sheet1.
'Close message after time if no action!
Dim myTimedBox As Object
Dim boxTime%, myExpired%, myOK%, myQuestBox%
'Access timed message box.
Set myTimedBox = CreateObject("WScript.Shell")
boxTime = 5
'Get user responce!
myQuestBox = myTimedBox.Popup("Click OK!" & vbCr & vbCr & "Or," & vbCr & _
vbCr & "Do nothing and this message will close in 5 seconds.", _
boxTime, "Select ""OK"" to Continue!", vbOKOnly)
'User Selected "OK."
If myQuestBox = 1 Then
'Add any code in place of code below for this condition!
myOK = myTimedBox.Popup("You Clicked OK!" & vbCr & vbCr & "Or," & vbCr & _
vbCr & "Do nothing and this message will close in 5 seconds.", _
boxTime, "You Took Action!", 0)
Else
'User took no Action!
myExpired = myTimedBox.Popup("You Did Not Click OK!" & vbCr & vbCr & "Or," & vbCr & _
vbCr & "Do nothing and this message will close in 5 seconds.", _
boxTime, "No Action Taken!", 0)
End If
End Sub