Override SWC classes in FB?

I have a Flash Pro project with numerous items in the Library linked to Class files.

I can successfully export a SWC and use the items in Flash Builder.

However, how would one override the Class in the SWC with a new one n FB?

Currently, to edit the Class, I have to open up the project in Flash Pro, edit the Class and export the SWC again. Only then will I see the changes.

When I try to put a new Class in Flash Builder with the same name as the one in the SWC, it will run that new Class but the assets of the Library item are not there.

Hopefully I am missing something obvious.