And I'm sure you're probably aware of
http://rubick.com/openacs/ad_form (which will be down this weekend)
But what I did on project-manager is available here:
http://cvs.openacs.org/cvs/openacs-4/contrib/packages/project-manager/
I'd look specifically at the add-edit.tcl file. The task-add-edit.tcl file doesn't actually edit, and the task-edit.tcl file only edits.
