Is it possible to simulate(Force I/O Values) the HW I/Os when the controller is online using excel VBA
You CANNOT do it with CB Open Interface. CB Open interface can only be used to create source code. You cannot write live values to a controller with CB-IF.
You can write to 800xA properties using Bulk Data Manager, but only if these properties are exposed and writable in Plant Explorer. The hardware channel IO variables are not directly writable.
You could write to the RealIO and BoolIO variables connected to the IO channel with BDM. This is not realistically going to give you a real time (or even close to real time) simulation.