How to block/limit what MIs are available to a master

[Walkerok]

I am writing a modbus slave and it is not something I usually do where I am not also writing the master. In this case it is a V570. I do not see any blocks available to me to only make certain MIs, MBs, Etc. available for read only or write only. I figure to prevent writes I can just store any MI values into secondary MI locations so the user won't have a valid address for a write, but it seems I am missing something here and it should not be so memory inefficient to get this done. There are also locations I do not want a user to ever be able to see what is in those locations.

Can one of you more experience minds out there give me some pointers so I do not do this stupidly.

Thank You

Keith