Determine If Page Refreshed

First I would question why you want to do this. If they get to the page by any means it should respond appropriately, whether refresh or by link. This is a stateless environment after all.

That being said...

I would take the approach of setting a session variable that gets set the first time they hit the page:

<%
if session("NotTheFirstTime") = "" then
'write the onload
session("NotTheFirstTime") = true
end if
%>

then based on that variable write or don't write the onload.

Of course, if the user can access the page from multiple links and the onload is valid for each link, regardless of how many times they hit the page, this won't work....