Option Explicit
Public counter As Range
Sub Start_Timer()
Set counter = Sheets(1).Range("z1")
Application.OnTime Now + TimeValue("00:00:01"), "CaR"
End Sub
Sub CaR()
Start_Timer
UserForm1.Show
counter.Value = counter.Value - TimeValue("00:00:01")
If counter.Value = 0 Then Application.OnTime Now + TimeValue("00:00:01"), "CaR", , False: _
Unload UserForm1: counter.Value = TimeSerial(0, 0, 20)
End Sub
Private Sub UserForm_QueryClose(Cancel As Integer, CloseMode As Integer)
If CloseMode = 0 Then Cancel = True
End Sub