I think that's going to be a bit tricky because when the MOSFET is not conducting you'll basically have 24V at point A. Feeding that to a PIC input is a not a good idea.

You'd need a differential amplifier across the resistor. That will amplify the difference between point B and point A and you feed that signal to the PIC's ADC.

With that said, is there a reason for not having the current sense resistor on the low side? That would make it easier since it's then referenced to ground. With a low enough value resistor it shouldn't have any considerabl effect on the gate drive voltage but you would still need to amplify the signal. However, that too is easier than a differential setup.

/Henrik.