Multiple trade prices?

Anyone out there got a work around to enable multiple trade prices?

I can display different 'trade' prices on the product page base on whether the user is logged in and has a specific tag e.g. trade25, traed30 &c. But can't pass that price on with the product to the cart.
If I just go with the standard trade_price (i.e. the single trade price functionality that ships with perch) all works OK.

Could I achieve the same thing bay applying a discount code? can this be done automatically?

Drew: Is this (multiple trade prices) something that could be included in release 4?