You might be able to change the wiring right in the switch box, but it depends how it was wired initially. There should be a "switch-leg", a black wire going up to the fan. You can get a tandem switch that is two switches on one strap to make this work. There is a "hot" wire coming in from the panel that should be attached to the existing switch. The other wire on the switch is the switch leg to the outlets. You can use the "Hot wire" (Usually black) for both switches then just put the appropriate switch leg on the load side of each switch.