I am replacing a foyer light with 3 switches[4way wiring] with a ceiling fan,[remote]and light kit.my question is how to wire it so all 3 switches will turn light off and on and still have constant power to fan

Please note the difference of the center switch -- and there are wires crossed on back of switch -- X pattern

http://www.electrical-online.com/Fall204.gif Click to enlarge picture

If you want constant power to fan you have to run a hot and neutral from where the

power enters the first switch all the way to the fan

If I understand correctly your existing light is controlled by two 3-way switches and a 4-way switch.
Just what you would have to do to replace this light with a fan/light combination with the light controlled by the switches and the fan controlled remotely depends.

It depends on where the power is coming in. If the existing light is being fed, that is power from the panel goes directly to the ceiling fixture box, all you will have to do is wire the fan hot wire to the hot wire coming into the box and connect the light hot wire to the switched leg. And of course connect the fan/light neutral to the house neutral. The wiring for the light of the fan/light combination would be identical to the wiring that currently exist for the light.

If one of the 3-way switches is being fed (has power directly to it from the panel) and if the switch leg to the light is in that same box, you will have replace the existing 2-conductor (3-wire) switch leg cable with 3-conductor (4-wire) cable.

If one of the 3-way switches is being fed and the other 3-way switch has the switch leg to the ceiling light fixture, you will have to replace all of the wiring between the two 3-way switches and the 4-way switch with 4-conductor cable and the switch leg with 3-conductor cable.

Sounds like you want two separate circuits-- a standard 4 way circuit (diagrams available online) to power the lights, and a single switch circuit, or constant hot, to power the motor.

You may get lucky and have a constant hot at fan to allow fan to be controlled by pull chain or remote. The light could then be switched from the 3 locations.