Create the sql query on session end

Hello everybody.
Sorry for my English.
I've created the temporary table, where I store logged users.
When user press logout button via sql I delete the logged user from this table. Problem appear only when user close web browser.
How to use sql  via session end. Below sql to delete user from temp table:
LblUserIDValue.Text = HttpContext.Current.User.Identity.Name.ToString <-system takes logged user(web auth)
 
deleteSQL = "delete from temp where loginuser= @user"
cmd.Parameters.AddWithValue("@user", LblUserIDValue.Text)


Thank you.

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