You could maybe add a field to one of the tables and then increment it by 1 each time someone enters the forums.
I would put the increment code into inc_top.asp and to stop it updating on everypage, I would check against a new session variable. If it is set, don't update. If it is not set, update first then set it.
in inc_top.asp (pseudo-code)
if newsession variable <> "" then
update count in database
set newsession variable = "anything"
else
do nothing
end if
Then as for showing the results, that bit is up to you where you want to show it but all you have to do is retrieve the count from the database and display it.
hths 
KatsKorner