I didn't notice the -type parameter in the proc you pointed me before:
https://openacs.org/api-doc/proc-view?proc=callback%3a%3asubsite%3a%3aurl%3a%3acontract, you're right I could have used that, I didn't know that when I started developing this package. I'll be improving this package along the way and that will be on top of my to-do list :D.
Thanks for the comments and suggestions.
