Dir. Network connection with user and password

Question

Hi.

I need to extabilish a network connection with 3 pc I know are on my network. Each one has a dir (always with the same name) shared. To prevent erroneous acces to those directories, the connection are accessible only by a user/password. When I use windows, I can connect, specifing the right user and password, but I don't know how to explain it to a C#.net program (who has to be used by onother user who hasn't to know the right user and password).

Someone can help me?