Need help using values from multiple columns to filter lists for data validation

Sadly, I can fumble through VBA better than I can figure out how to do things the normal formula way.

I have tried combinations of match, vlookup, and index. But I can't seem to find a definitive source on the best way to approach my solution.

Basically, I have a fat range of data (sheet "ALL_PARTS"). With 3 columns I'm really interested in to start with.

The first column categorizes the equipment.
The second column has the manufacturer.
And the third column has the part numbers.

On a data entry sheet (sheet "EQUIPMENT"), I want to use data validation to filter the list at each stage.
screen-cap.JPG

Step one: select category.
Step two: select manufacturer (filtered down based on the category)
Step three: select a part number (filtered down based on manufacturer and category)

Step four (already figured this part out): Match the part number to values in the range and populate the columns on the data entry sheet.

I can't figure out how to do it. And I've searched on here, and I've gotten close, but when I look at people's formulas my head starts to spin.

Anyway. Attached is my Excel. With some fun VBA for pulling and sorting data. Just can't figure out how to make things work on the EQUIPMENT sheet...


AV Cost Estimate Template File - no costs.xlsm