I assume the walls are open right now.

It really depends on where the power enters the present setup - at the switch or at the recept. If at the switch, you only need to add a new run to the ceiling and reconnect the run to the recept across the incoming feed. If at the recept, the switchloop becomes a feed to the switch.

You may need a larger box at the switch to handle the extra cable and stay within box fill rules.

It sounds like you might benefit from some quick and dirty education in basic electricity and circuits. If you have Wiring Simplified, reread the basic electricity chapter. If not, I suggest a trip to the bookstore or your nearby Home Depot.