Price default in PR/PO and Back to Back PR

 Item supplier currency is different from the functional currency. The standard purchase price and the UOM for an item can be captured in the Approved Supplier using a quotation and defaulted in the PR and PO created directly. But the supplier supplies at a special price based on customers (price varies for each customer). Is it possible to have the supplier price captured against a customer and whenever Back to Back PR is created can this special price be defaulted automatically and at the same time when a direct PR/PO is created, the standard price should be defaulted. Is it possible to