Combo box filtering (1 Viewer)

Hello

I have a web database. There are couple of tables with lookup fields ( first one called department where all department codes are stored and the second one where there is a look up field department from department table and other fields like names and so on ... )
I need to click on specific department button on one form which would open another form with combo box with all the names populated from that specific department.

Any help or direction is most appreciated

Thanks