HOW: purchasing info record price + markup in % = sales price

Dear all,

at the moment I’m looking for a solution of the following problem:

We will create a special sales document type for selling spare parts.

The sales price for the spare parts has to be the price from the purchasing info record + always 25% markup.

How could I realize that the sales price is price from purchasing info record + always 25% markup.

(We want to avoid that we have to change the sales condition records manually, if purchase price is changing)

Thank you very much for your help.