I agree with Dave. But the approach to take really depends on what it is you need to do in
between the LED on\off periods, how long the LED should be on AND off, the oscillator speed,
and which PIC you're using.

Trying to work out the number of if-thens between toggling the LED on or off isn't a very
good approach, since the time will vary as your code in between the on\off periods will
change, and require recalibration with every change.

More information would really help folks here to help you..;o}