insert to sql database from asax

I want to try to count the number of open sessions on my site. What I hope to do is insert to a sql database from the global.asax file and add 1 to the database field "sessions" on session start in the global.asax and then subtract 1 when the session ends. my problem is that I dont know how to put the "using System.Data.SqlClient;" into the global.asax file so that I can do an insert to the database. I know its pobably a dumb qusetion, but I'm new and trying to learn. Im using VWD 2005 Express with c# code bechind and SQL server 2005 Express on a IIS 6.0 server. Thanks for your help.