SSL VPN question

Hi!

Please help 

FortiOS 5.2, I need implement secure access to internal file server via latest Forticlient and SSL VPN. I made SSL VPN setup with AD auth (group), client connect perfect, all work fine, but when I try access file server via Forticlient connection, windows server ask me for login password. When I enter user name / pass - all work fine.

Question, how make access to file server without additional login/pass enter via SSL VPN after connection via SSL VPN? Like was in MS TMG (RIP). Doe's it possible with FortiGate ?

Txn for help!