Bill of Materials

Check Table filter feature
If you filter Mtg all the next filters show values assigned only to first choice, next if you select any value in Function, (so we have two filtered values) all the next filters show values assigned only to first and second selection, etc...

You can try with Pivot Table but this is very similar to table filtering

Maybe someone else will give solution with formula(s)

edit:
btw. you didn't show what you want to achieve

on the end you may use Commercial Service