Reference a non logged in user with user.isinrole

Hi

I need to reference roles for a user other than the current user, whilst logged into a web app. I'm looking for something like

If User("Username").isinrole then
     Do something
End If

Obviously, above syntax is incorrect and it won't take the username variable. Is there a way to achieve this? To reiterate, I am not interested in the roles for current user.

Thanks

Steve