Disable Drop Menu When Criteria Is Met?

[Margate]

Hello Everyone,
I have a validation drop menu (data / validation / settings / list) that I want to disable when one date is greater than another date. So for example today is 5th November but I want the drop menu to disable when the date is 6th November. Cell C1 contains a start date (can be any date at all) and cell D1 contains today's date

=TODAY()

.

The source for the contents of the drop menu is A1:A5 and the actual drop menu is in cell B1. The drop menu contains just numbers from 1-5 (including both 1 & 5). Whenever one of these numbers is selected from the drop menu a macro is called using the following code:

Private Sub Worksheet_Change(ByVal Target As Range)
If Target.Count > 1 Then Exit Sub
If Not Intersect(Target, Range("C6")) Is Nothing Then
  Select Case Target.Value
    Case 1
      Call DayOne
    Case 2
      Call DayTwo
    Case 3
      Call DayThree
    Case 4
      Call DayFour
    Case 5
      Call DayFive
  End Select
End If

Each number (1-5) calls a macro that just hides / un-hides the numbers of rows that are visible on the sheet.
Is there any way to perhaps add a couple of lines into the above code or an easier way to disable this as soon as the day expires? All I want to do is to prevent the drop meun from being usable any what possible. I tried using if statements but to no avail!

Thank you very much for any help

Margate