digital pots and arduino

I am working on a school project where we have an arduino decimilia wired up to a xbee transciever. We have them communicated on a basic level properly, when we stitch a switch on the transmitter an led will turn on at the reciever pin 11. We want to use a digital potentiometer to wirelessly change gain of the signal input.

we are using the CAT5115 digital pot which has the pin connections Vcc, GND, Inc, Up/down, Rh, Rl, Rw, CS. We have the Vcc, Rh hooked up to 5v and Gnd, Rl and CS(not) to ground.

we have our output pin on the arduino programmed for 11 and run that to the Increment pin and a led testing the status on the Rwiper. We want the led to get brighter on the wiper resistor the more we switch the switch. Any ideas of why this isn't working, or a better way to connect a digital pot. to the arduino to make it more simple.

thanks in advance

Joe