Rotation sense of a potentiometer
Normally a potmeter has three connections. The middle is the wiper which moves over the resistive path, from the left pin to the right one when rotating clockwise. Swap the left and right pin and you should be OK. Important: be sure that it's a logarithmic potmeter instead of the regular linear ones.  

edit
I read that the resistance increases if you rotate clockwise, and that you want the reverse. I don't know what the surroundings of the potmeter look like, but for a volume control you normally want to increase the resistance (between the left pin and the wiper) when rotating clockwise. If for some reason you want the reverse you don't want a logarithmic potmeter, but an anti-logarithmic one, which is much rarer.