This was suggested by Jose Carlos some time ago and works just great:
If you have the NT Resource kit, you can use the SOON utility. It
schedules a command to run after a given number of seconds.
Let's suppose you want to run the MRTG command located in the C:\MRTG
folder every 5 minutes. You can create a batch file called MRTG.CMD
or MRTG.BAT, and place it in the C:\WINNT\SYSTEM32 folder:
SOON 300 MRTG.CMD
Then, you will need to call this batch file once and it will
schedule itself to run again after 5 minutes and each instance will
re-schedule the job automatically.
Hope this helps,