I've read though the Multi-Field plugin and it seems quite interesting. But I have an issue trying to link a field to a category.
Heres the steps of what I want to do.

1) An agent click on "Add a Listing"
2) The agent chooses the category (the province)
3) He selects a plan
4) In the information form, I would like to have a dropdown that would be linked (generate regions) depending on the category selected earlier.