Assuming that you have a table somewhere (say columns M and N)
comprising:

1 ONE
2 TWO
3 THREE

etc., let's say up to row 10, then in B1 you can use this formula;

=VLOOKUP(A1,M$1:N$10,2,0)

The drop-down in cell A1 (I presume you mean by Data Validation) can
use M1:M10 as the source list, so that it must be found in the table.

Hope this helps.

Pete

On Sep 29, 1:18 am, Brad wrote:
I have some cells you can select using a dropdown list using conditional
formatting, and I want to be able to populae the next cell depending on what
was selected but I don't know how to do it.

For example, if 1 is selected on cell A1 on the dropdown list, I want cell
B1 to automatically fill in ONE based on another list in the same workbook on
a different sheet...But I don't know how to do this - can anyone help me out
here? Thanks.