I'm guessing you have it login to start some programs? Why not just call the lock screen function during startup of the user that logs in automatically? This would let it auto login and start a program, but immediately lock the screen.
Shortcut would be “C:\Windows\System32\rundll32.exe user32.dll,LockWorkStation”
If you're just talking about the login screen's screen saver... you should be able to use the default user settings that apply to the login screen to accomplish this.
This should apply:
https://support.microsoft.com/en-us/kb/185348
Set your screen saver along with a 1 minute timeout