OK, stupid question time, did you have it running for any length of time after changing the belt?
Pull the distributor cap and see if the rotor is spinning. If so, and your sure the coil is firing correctly. Then you'll have to turn the motor until you have the number one cylinder at TDC after the compression stroke. Then rotate the distributor until the closest vane is just crossing the gap in the pick-up. That should get you close enough to start the engine.