Sounds like you are in Manual calculation mode:
Tools--Options--Calculation check Automatic

regards
Charles
__________________________________________________
The Excel Calculation Site
http://www.decisionmodels.com

"Code Numpty" wrote in message
...
Excel 2003 - I have a VLOOKUP formula which I have copied down the column.
When I check the formula it has copied down correctly, yet the result
returned is that for the first cell in the column for every single one.

To get the correct result I have to double-click every single cell
containing the formula, which will then show the correct result.

This has only started happening recently. Has Excel corrupted in some way?