I have a table called

table1

and another two tables called

regions,
territories

territories all have a FK of region (i.e territories belong to a region)

Table1 has two cross reference tables

table1 - regions (n:n)
table1 - territories (n:)

and using the pivot method built into J-Cook builder by default

I want to make it so that a person chooses REGIONS first when completing table1 (multiselect, entries go into table1region XRef table), but then in the next field, rather than being able to multselect ALL TERRITORIES, they are only presented with those that belong to any selected regions.

I can obviously fire an auto save when a user adds regions, but quite sure what model to alter to build in the complex join for the territories XRef

Any advise greatly appreciated