Um.. Couple of things.
Regarding scheduling a task to repeat on a scheduled interval - YES, this is possible with JT.exe. Download my tsAdm package from KixForms.org (which includes tsControl library, documentation, and sample scripts) to see an example.
The sample script in the zip file also creates a repeating task. Just a few lines of code using tsControl.
Also, with regard to setting user credentials for task events with JT. The same tools and samples illustrate how to do this. I regularly use tsadm to schedule tasks with account credentials other than my own. Sometimes when I'm connected by terminal server and sometimes when I have a drive mapped. Doesn't matter!
The tsControl/tsAdm package (.zip) is also available on NTDoc's and Radimus' web sites.
Glenn
_________________________
Actually I
am a Rocket Scientist!