Changing an altitude for IAP in FMS

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Hello,

I was flying with a guy who says you can't modify an IAP that is pulled from an FMS. I agree you cant modify the waypoints but he claims you cant modify the altitude. I always change the altitude in the FMS if there is a NOTAM giving a new altitude. He claims the only allowance to change altitudes for a retrievable procedure is for STARS (reference: AIM). I am trying to find a reference for changing a segmet altitude on an IAP but I am not having much luck.

Any ideas where to look?

Thanks