Dual base currencies setp

I have Magento setup with dual base currencies (CAD and USD), there are two stores, one for each currency. When adding a new product it takes the currency conversion rate into consideration and creates the product with their own two distinctive pricing. However if the rate changes it does not update the price, also, any product created prior to implementing the dual base currencies have the same pricing for USD and CAD. Is there a setting I'm missing to update pricing for CAD based on the USD conversion rate?