Many to may relation with Activities/todo

[radu]

Hello,
I need some help. I want to relate the module Project to the ToDo's(Activities) in a many to many relation. If i just add the todo module to the related lists in Project's Layout, the table is empty and no buttons to add anything. I found this in wiki related to this issue:
" Activities is done like this:

setRelatedList(relatedmodule, header, actions, 'get_activities')"

But i don't know how exactly to do it. If I do a php with that
setRelatedList(Project, header, actions, 'get_activities')
it just throws
Fatal error: Uncaught Error: Call to undefined function setRelatedList()

Any help is appreciated.

Thanks