Take a look at Microchips Application Note AN592

Frequency Counter Using PIC16C5x

http://www.microchip.com/stellent/id...pnote=en011033

Supposedly this will work up to 50Mhz, although I haven't tried it myself.

I also assume it can be applied to a 16F876, since the timer0 modules are pretty much the same thing.

And, here's a link to a project where somebody applied AN592 to a 16F84.
http://digilander.libero.it/ik3oil/_...o_eng_2003.pdf

HTH,
   Darrel