Asp.net, vb.net global variables.

I am using visual basic dot net, with the asp.net add on. I have created a programme which works great, basically it has a logon, which uses mysql for the data, then loads a 2nd page using the username data. I am using the global variable to store the username between pages. Its all good, untill another person logs in at the same time as the first user, now when they log on, user 1 now has the globale variable of the 2nd user.
What I need is a globale variable that is unique to each user. Any idea how this is done, I am very new to asp.net.