Window Exhaust Fan instead of Air Return

I am in a 100 year old house with a lower level, main floor and 2nd floor. We have a Forced Air furnace. Each room in the house has a vent. However, there are only air returns on the lower level and main floor. I am considering installing central AC but am concerned that the 2nd floor may not cool sufficiently without any air circulation. Is it an option to run a window exhaust fan while the AC is running to force air out of the room that can be replaced with the cool air from the vent?

Is there a better solution?

Thanks

source https://hvac-talk.com/vbb/threads/2227290-Window-Exhaust-Fan-instead-of-Air-Return?goto=newpost