I need help urgently!!

I have a large Inventory Database that needs to consist of Over 1400 sub categories.. These I have managed to break down into 3 tables.. Product Categories (for parent Categories), SubA (For sub-categories of "Product Categories") and SubB (for sub-categories of "SubA").

What I now need to do is create forms for using these categories and subs to give each product the appropriete values in combo boxes labled "ProductCategories", "SubA", and "SubB". However, these need to be preformed on forms for editing products, searching for products, and ordering products.

Can anyone give me examples on how I do this for each type of form. Ideally, "SubB" combos need to be filtered by selection of "SubA", and "SubA" Filtered by selection of "ProductCategories".

In the editing form, these selections will be stored in the appropriate fields for the category and sub categories of the product names.

In the Search form, the Category and sub categories fields will determin the list of products in those categories and sub categories (that exactly match the selections).

And in the Order form, the user will use the combo boxes to place product names into a listbox depending on categories and subcategory selections (the listbox will show the product names of relevant products, and the user will select from this listbox to "autofill" details for the order depending on the product record selected in that listbox).

Can anyone help me with all this??