You might be able to get some dodgy bit of firmware which will do it , but this will without certainty invalidate the warranty and if your PS3 'bricks' (i.e. becomes unusable due to the code in unofficial firmware) you'll be left with an expensive paper weight. Also, you could never update your firmware with Sony's official updates as this would replace any region free code built in and also increase the chance of bricking the console.
So not really worth it, just get a cheap region free DVD player for your existing other region DVDs and only get region B or region free Blu-Ray titles - there are an awful lot of films on Blu-Ray which are actually region free.