Automatic pricing updates

[Joe F]

Hi all - is it possible to configure Prestashop or buy a module so that I can define product pricing in terms like "3.5 x variable X' or 'variable Y + $20'?

I have a friend who wants to define their pricing relative to a base price obtained from an XML feed e.g. product A costs twice as much as the base price, and product B costs $20 plus three times the base price.

An alternative to using a feed would be to update the base price daily in one place in the admin area and have all prices on the site update accordingly. In a way this is similar to setting the exchange rate between currencies, though not identical obviously.

Any ideas or suggestions?