Never tested and I think it won't work but just an idea....
if(osuser()= 'DOMAIN\USER1', Sum (Value),
if(osuser()= 'DOMAIN\USER2', Sum (Rates)))
Usually you cannot hide the column unless it is Section Access OMIT field
unless you write a new security rule in QMC but that would disable the object based on user name and not column.
Have you looked into Container?
I think there is an extension for Conditional Hide/Show of charts within the container.