SSAS security for calculations

Hey I’ve a cube where I’d like to implement security access on different measures and calculated members

I've a calculation named profit which is derived from [Measures].[sales] - [Measures].[Cost]

Profit = [Measures].[sale] - [Measures].[Cost]

Question 1: How do I get the calculation named profit displayed in the Dimension Data cell security access so I can disable the Profit
cell.

Question 2: If I disable the calculation named profit which uses the 2 measures sales and cost will this impact of the sales & cost cells from displaying

                       From read up does enable read –contingent on a cell security get me around this problem ?

                       Will the below MDX work for this example

( Measures.CurrentMember IS [Measures].[Sales]) and ( Measures.CurrentMember IS [Measures].[Cost]

Thanks