You can do this with Data Validation. Select the cell whose entry you
want to restrict. Open Data Validation dialog from the Data menu,
choose "Custom" on the Allow list, and enter
=LEN($D$1)>0
where $D$1 is the cell which must have data in it in order to enter
data in to the validated cell.
Cordially,
Chip Pearson
Microsoft Most Valuable Professional,
Excel, 1998 - 2010
Pearson Software Consulting, LLC www.cpearson.com
