Place this code at the top of your asp page for it to work.
[%
Response.ExpiresAbsolute = #2003-01-01#
Response.AddHeader "pragma", "no-cache"
Response.AddHeader "cache-control", "private, no-cache, must-revalidate"
%]
Replace the [] with <> if you find that the page is caching then it's IIS that's doing it!