Just to add to Peo's suggestion.
If you're using xl2k or above, Peo's suggestion will work fine.
If you're using xl2002+, there's an option to search through the workbook on the
Edit|Find dialog.
And if you're using xl97, you may want to try Jan Karel Pieterse's FlexFind:
http://www.oaltd.co.uk/MVP/
(It'll actually work in all these versions.)