Can I piggy back a bath fan light onto another bath light fixture?

[skunther]

My problem is this:

I have 2 sets of Romex 14/3 in my bathroom - one going to a light fixture, and one going to a bath fan unit (both set into the attic space). I am replacing the fan unit with another that has an integrated light (which we sorely need - the existing light fixture is poorly placed). I don't have a dedicated wire aready run for the fan light though, and do not want to rip up the drywall to rewire the bathroom to accomodate it. Can I simply piggyback the bath fan light to the existing bath light fixture (run the load and neutral from the existing fixture to the bath fan light through the attic), or does this create fire hazard/other problems?

On a side note, if this wiring arrangement is viable, would it also be viable to run only the light switch load line from the existing fixture to the bath fan light (and not the neutral), using for the light's neutral the one that routes back from the fan? Or does the neutral need to be paired with the same hot line that feeds the load?

I would like to be able to have all the lights (including the bath fan light) work off one switch, and the fan work of a dedicated fan switch.

Thanks -