Automatically Save Workbook Every X Minutes

I've created a MsgBox that if you do not respond or Click on it within a set time it will either disappear or perform an action upon no selection. It works great....IF it’s the only excel workbook open. If there is a second workbook open (Even if the second WB is minimized) then the MsgBox just stays up and the "Timer" no longer works. My Code is as Follows:


Sub TimedMsgBox()
Dim Box As Object
Dim varResponse As Variant
Dim Res As Long
Set Box = CreateObject("WScript.Shell")

varResponse = Box.Popup(Text:="Which button will you click?", secondstowait:=5, Title:="Click Me!", Type:=vbYesNoCancel)
If varResponse = vbYes Then
MsgBox "You clicked Yes"
ElseIf varResponse = vbNo Then
MsgBox "You clicked No"
ElseIf varResponse = vbCancel Then
MsgBox "You clicked Cancel"
ElseIf varResponse = -1 Then
Res = Box.Popup(Text:="What? Do you not like me?", secondstowait:=5, Title:="You Didn't click Me!", Type:=vbOK)
End If
End Sub