well, i wish i could guide
anyways, have you been to neelan bhoto village in margalla..
from pir sohawa ask any one about this village. when u get on the road to neelan bhoto, after about 15 to 20 min drive, you will reach where this track folks. take the left folk that goes down hill. proceeding on that track u will reach a place where road is broken, ask any one there to show u waterfall....
all biking and a bit of scrambling...