I have a worksheet containing project-related information. In particular:

Column D = Status Code (0 - 20); Code "11" = On-Hold, Code "12" = Cancelled
Column DT = Project Hold Date
Column DU = Project Un-Hold Date
Column DV = Project Cancelled Date
Column DW = Project Un-Cancelled Date

I'm trying to write a macro whereby if a user inputs Code "11" in Column D
for a given project, the current date would automatically be entered in
Column DT. Later on, if the Code is changed to anything but Code 11 (except
for Code 12), the current date would automatically be entered into Column DU.

If a user inputs Code "12" in Column D for a given project, the current date
would automatically be entered in Column DV. Later on, if the Code is
changed to anything but Code 12 (except for Code 11), the current date would
automatically be entered into Column DW.

Also, it would be nice if the macro displayed an error message if a user
attempts to indicate that a project is on Hold or Cancelled more than once
(i.e., check to see if columns DT - DW already contain a date).

Any help would be greatly appreciated.
Thanks,
Bob