how to calculate quantities used using manufacturer part code

[funtimex12]

Hi, i need to make sure the wording matches and then reduce the quantity on the left by the quantity on the right.  Is there a simple way to do this please? As wording are not always going to be on the same line. 

			Equipment used:
Parts Description	Manufacturer Part Code	Supplier	Quantity	Parts Description	Manufacturer Part Code	Supplier:
apollo xpp95 addressable smoke detector	55000-600APO	ADI	50	apollo xpp95 addressable smoke detector	55000-600APO	ADI
apollo xp95 manual call point	SA5900-908APO	ADI	100	apollo xp95 manual call point	SA5900-908APO	ADI

[#2]

as the manufacturer part code on the right needs to 'find' the manufacturer part code on the lef, see the quantity mount next to it and then reduce in a new column

[#3]

@funtimex12 

I don't see a quantity on the right...

[#4]

@Hans Vogelaar there’s one on the right the one on the left is missing but it’s Column A 

[#5]

@funtimex12 

I'd use a separate column so that you can see the original stock. See the attached workbook.