Private Sub Worksheet_Change(ByVal Target As Range)
If Intersect(Target, Range("A1:A20")) Is Nothing Then Exit Sub
UserInput = Target.Value
On Error Resume Next
If UserInput > 1 Then
NewInput = Left(UserInput, Len(UserInput) - 2) & ":" & Right(UserInput, 2)
Application.EnableEvents = False
Target = NewInput
Application.EnableEvents = True
End If
End Sub