Attempting to link 2 drop boxes

[lizzybug0802]

After a lot of fighting with the software, I am completely lost how to get this program to link 2 drop boxes. I have the data listed in an excel form and the document fully built out but I am stuck from there. I have attached an image of the problem, I am attempting to link the division to the department drop box so that each division has only their departments showing. Please help!