HVAC issues

I went out and looked at the vent doors today. It turns out that the outside air door is directly linked to the heater core bypass door. In other words, the only possible way for air to flow through the heater core is by having the door to the outside air open and the bypass door under the heater core closed. I was trying to think of a way to close off the cowl so that I could open the fresh-air door on the right side so the fan would suck in air from the inside instead of down from the outside through the cowl. If you get what I mean...