Not sure if I understand your question correctly, but after asking the user name and password, you can start a new process with the given user account. You just need to use the
ProcessStartInfo[
^] to define the user name and the password.
I used a similar technique in
Directory size browser[
^]. Have a look at the code in "Option 2: Elevate privileges during the application startup".
Again, sorry if I misunderstood the situation.