You may be able to adapt the technique shown he

http://www.contextures.com/xlDataVal03.html

wrote:
I have a work sheet with a list of numbers
I set up a Data Validation in several cells that "links" to this
list
Once I pick a # form the list I do not want to be able to pick it
again.

Ideas?



--
Debra Dalgleish
Contextures
http://www.contextures.com/tiptech.html