NT server Back up

Hi,
Any one can help me configuring the back up with NT Server 4.
I got dual HP Net server (New) and I installed, every thing it ok, the back up I can do manual but what about automatic, I know some software can do but my budget can’t afford to buy it. I got scrips of WINT NT Server for back up thing, but I don’t know how to make the AT.EXE to operate with schedule and configuration it automatic.
Thanks for your help. As soon as posible please.
Thom