PIC MCU: Two ADC inputs help
With this PIC true simultaneity is not possible, as there is only one sample and hold and one converter. If nearly is good enough, then adjusting your code to simply switch between inputs would work. If not, then a PIC with more than one ADC/Sample and Holds would be the way to go, e.g. a dsPIC such as the dsPIC33FJ128GP802. 
Or of course you could add an external ADC.