Freezing the prices once in my Cart

I'm just wondering if I can do the following with rules (rather than having to write a module):

* I'm building a site where the prices of products update every minute.
* When a user adds a product into their cart I want that price to 'freeze'.
* So when the product updates in the background the old prices remains in the cart.
* The price remains frozen for up to two hours

The trouble I'm having is setting the variable. It would seem the best place would be to set the variable upon adding an item to the cart. But I need another rule for calculating the sell price for the user. The variable isn't carried from one rule to another.

Any suggestions or advice would be greatly appreciated.


Posted: Mar 5, 2012