VLOOKUP with hierarchy of options

Hi guys, I am trying to put a formulae together that incorporates a subcategory when I do a vlookup. I have a supplier code, each supplier has a product group, this group then has a discount associated to it. I am trying to put into one formulae the search of a supplier code and group if there is one to show the discount in place. Some product groups also cover a few suppliers because they are generic items. the vlookup I am using is here:
=(VLOOKUP(H5,'DISCOUNTS PER GROUP'!$A$1:$J$2431,8,FALSE))

say my supplier code is 1 it may have discount groups a, b, c attached to it, supplier 2 might have discount groups b, c, d. I have built a sheet that has each supplier with the discount codes within them. so I have duplicated the discount groups.

Thank you in advance guys

SB