Advice and code sample

I need some help with my task, hopefully someone out there had done this before and don't mind sharing.

My department is using a Visual Basic app (this app is here since before I came) and a CF web app (I'm responsible for this one).

The CF app is a supplement to the VB app. Any functionality that is not in VB app. is created in CF so user can go back and forth between the two app. This VB app is maintain by sunggard and it's quite complicated.

Now Sunggard is changing it into dot net web app, the VB need to retire. We'll end up with 2 web apps, one dot net and one CF

Both apps use the same tables/DB.

User use the same username and password to login to both apps.,The password is hashed.

Is it possible to combine both application in the login process level? meaning, when users log in to either one app they can access both app without having to login twice at 2 different places like now? how can I achieve this goal? some sample codes is really helpful. I'm not a dot net developer, I'm hired to do CF so I'm not familiar with dot net.