Do you know how to set up a conditional value list? If not:
The cute trick we can play with your check box field here, is that a list of values in a check field can be used in a relationship to get related records that match any one of the listed values.
Say you have two checkbox category fields in this relationship:
Master::CheckBoxField = Projects::CheckBoxField.
You'll find that for any given record in Master, it will match to any Projects record where at least one selected value matches at least one selected value in CheckBoxField of the current Master table record. This relationship, can then be used as the basis for a conditional value list such as those described in the two threads I've provided links to.
Thanks for this. I've jus tried it out and it worked beautifully. Really excellent advice! Many thanks.