buckworks - 7:34 pm on Feb 8, 2011 (gmt 0)
Sally, check how much editing is possible within your AdSense account.
Go to AdSense Setup >> Manage Ads, select a channel to edit, and you can specify alternate ads in there.
Your comment sounds like you're not using includes for your AdSense code. That's well worth considering, because include files can be reused on as many pages as you want which can then be updated by editing just the one file.