Private Sub Worksheet_Change(ByVal Target As Range)
Dim ThisColumn As Integer
Dim UserInput As String, NewInput As String
ThisColumn = Target.Column
If ThisColumn < 3 Then
UserInput = Target.Value
If UserInput > 1 Then
NewInput = Left(UserInput, Len(UserInput) - 2) & ":" & _
Right(UserInput, 2)
Application.EnableEvents = False
Target = NewInput
Application.EnableEvents = True
End If
End If
End Sub