Hi,
You can count it like it's a button but the way you have it now means that the pulses have to come in exactly during the 60ms you're actually counting. If they start to come before you start to count you'll miss some of them or if the pusles starts 30ms after you've started to count you might stop counting before all pulses have arrived.

Just look at the datasheet for the PIC you're using, TMR0 is probably the easiest to use. Read the section, look at the T0CON register and you'll see how to configure it as a counter. The pulses then goes to T0CKI-pin and you can access the count by reading the TMR0 register.

Give it a try, if it doesn't work post the code (and what PIC you're using) and we'll take a look at it.

/Henrik.