Keith --
Create a 2-column list in some worksheet consisting of names and corresponding phone numbers.
Select all the cells where you have the names and name it e.g., NAMES via the name Box on the Formula Bar (Don't include any label in the selection). Select now all of the cells of the 2-column list and name it, e.g., PHONES via the Name Box.
In a relevant cell in some sheet, say A1, construct a dropdown list. In order to do so,
activate A3;
activate Data|Validation;
Choose List for Allow;
Enter as Source
=NAMES
and click OK.
In C1 enter: =VLOOKUP(A3,PHONES,2,0)
Aladin
==========
Thank you Aladin you suggestion works really good.