the problem with using the pause statement is that it effectively halts the execution of the rest of the code until the period has elapsed.

How many LEDs do you want to fade up and down? There are dedicated LED controllers that use i2c to communicate with the PIC, that can handle multiples of 16 LEDs, and means that once you have sent the value off to the chip, the PIC can the perform other functions.

Post up what code you have and more details on what you are hoping to achieve and I'm sure you'll get some suggestions