Save and display data from 3 dependent combo boxes

[oxicottin]

Hello, I'm having trouble understanding how to save data from my 3 combo boxes in form frmVWI (cboDepartment, cboCategories, cboSubcategories). If you look at the image the form uses (tbl_VWI) and I can save the data from cboSubcategories with SubcategoriesID but how do I save the others to my table tbl_VWI? what do I need to add to the tables and relationships to achieve this? I attached my relationship image and my DB broke down for the example.