Ways to Set Maximum OA for a System

[terrichow]

I am modelling for a system with a PAU(primary air handling unit) (or DOAS in IESVE)+ AHU + VAV, which means the OA drawn into the building is somehow limited by the PAU equipment air flow rate.
When utilising DCV, it allows the OA to modulate according to indoor CO2, but technically for my system, the OA would not be able to exceed the air flow rate of the PAU.
I understood that the inputting the design flow rate in the supply fan and cooling coil does not affect the actual flow rates. Are there anyway I could set a maximum to the system OA?