Identify Which Session Variable Expire

i have 2 application variables called totalAdminLoggedIn and totalUserLoggedIn

when ever an admin login, I increment the totalAdminLoggedIn value by one
and when a normal user logg in, the totalUserLoggedIn value will be incremented by one.


how can i change the values when the session expire ? i can reduce the value manually when they logoff like:

if session("userCategory")="admin" then
Application("totalAdminLoggedIn")=Application("totalAdminLoggedIN")-1
elseif session("userCategory")="user" then
Application("totalUserLoggedIn")=Application("totalUserLoggedIn")-1
end if
session.contents.remove "userCategory"

but what if the session expires automatically or if they close the window suddenly?

ie. i want to do something like below? Code: