You can Add WatchPoint during debug session on Read , Write and Access for the Port Registers
How? I still can't get this to work.
Taking your example given, you can see this register in SO.h file:
#define SO_PS (* (reg8 *) SO__PS)
If during debug, you right click this, are you not getting the option of "Add WatchPoint".I checked in Creator4.2. Presently, I don't have Creator4.0.