The problem is not the speed/frequency of the signal. 100Hz and 1000Hz isn't all that fast, especially to a 30+MHz clock PIC. The signal is analog, not digital, and it's not at all clean.

If it were a nice clean square wave, PULSIN would do the job great. But it's a distorted sine wave combined with a great deal of white noise.

Thanks for the reply, at any rate,

Mike