o googlu už jsi slyšel? Já tuhle službu právě vyzkoušel a vážně funguje!
EDIT:

Sub VlozCas()
Cells(1, 1) = Time()
Application.OnTime EarliestTime:=Now + TimeValue(\\\\\\\"00:00:01\\\\\\\"), Procedure:=\\\\\\\"VlozCas\\\\\\\"
Cells(1, 2) = Now + TimeValue(\\\\\\\"00:00:01\\\\\\\")
End Sub

Sub Konec()
Application.OnTime EarliestTime:=Cells(1, 2), Procedure:=\\\\\\\"VlozCas\\\\\\\", Schedule:=False
End Sub