We have two custom objects A and B which have a many-to-many relationship so they have a junction object J to connect them. Now I am having another custom object C which has lookup field to both A and B. In object C, for field B, I want to implement a lookup filter which requires the picked B has to have a relationship with the choosen A in C object. Is it possible to implement this using lookup filter or something similar. Trigger doesn't seem to be a very nice option though because in the page level it still displays all the options, not just the available ones.