If Dell gave you a DVI cable with the monitor, that should work just fine. If, for some reason, you think you're having a problem, you should post that instead.
All DVI cables are identical in functionality and picture quality; since the signal is digital and not analog, it is not susceptible to electromagnetic interference like VGA is, so between cables the only real difference is sturdiness. I recommend you look at a cable from Monoprice, as I hear they have excellent prices.