calculate a varchar

Is there a calculation function? I'm using an e-commerce shopping cart. I want to tweak the code. The author is using a varchar(100) field to store prices. Taking advantage of there being a varchar, instead of entering a price, I would like to enter a calculation. (24*2.2)+(24*2.2*.1) 24 is my unit price in British pounds. 2.2 is the exchange rate into Canadian dollars. etc. The exchange rate changes frequently. Instead of recalculating and entering a new price every few days, it would be useful to enter a calculation in any price field. I had a look at: http://ca3.php.net/manual-lookup.php?pattern=calc http://ca3.php.net/manual-lookup.php?pattern=calculate http://ca3.php.net/manual-lookup.php?pattern=calculation but I see no function, although I'm sure there is one. So how could I do this? $price = (24*2.2)+(24*2.2*.1); if $price is not an integer, verify if it is a calculation. If so, give me an integer and round it off to two decimal points: $price = 58.08; Do-able? John