Group Price Scenario

Hi

I have been asked to create a modifier to cover the following scenario:

ProductA, ProductB, ProductC, ProductD, ProductE

If a combination of any of the above are ordered

5 x @ Price1

10 x @ Price2

15 x @ Price3

These items are on a list price price list containing thousands of other products

A large quantity of customers are entitled to this offer

Ideally I would prefer not to put them on a separate price list as our price lists are already quite heavily nested so this could create a great deal of work assigning to customers etc

Any help would be greatly appreciated