Try this:
Put the 25 zip codes in a vertical list on another sheet in the workbook.
Name that list:
Select the 25 cells, then
In the Name box (Just above the Col_A heading) enter: LU_ZipList
Press [Enter]
Now, select an input cell (I'll use A2)
Format>Conditional Formatting
Select: "Formula Is" from the dropdown
Formula: =ISNUMBER(MATCH(A2,LU_ZipList,0))
(Note: No dollar signs in the A2 reference)
Click the [Format] button and set the display to show for zips on the list
Click the [OK] button
Now copy A2 down as far as you need.
When you enter a Zip Code that is on the list....your conditional format
will display.
Does that help?
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Regards,
Ron