Can this be used to populate options in Separate Class for Fields?

[dan-lutd]

I have a locations resource that has a M2M relationship with Vendors and the pivot table has a select for the Distribution Centers (DCs) of Vendors. I can save the values OK and it works for what we need except the Select shows all the DCs and I cannot figure out how to show only the DCs of the vendor chosen.

Detail here: Stack overflow question