MDX Dynamic Code on execute

Hey

I have an SSRS report , 3 options (Parameters the user selects on runtime, non multi value) , based on

Option 1 (Default) -- Result set returns based on the Activation date period 

Option 2               -- Result set returns based on the Bound date period

Option 3               -- Result set returns based on the Fulfillment date period

What I want to do is

If the User Selects Option 1 the MDX query will run based on the Activation date period , Option 2 based on the Bound date period etc (only one option allowed at a given time)

What is the best approach to take, I am thinking the IIF Statement;

So

IIF (@Parameter =1 , [Date].[ActivationDate]),

IIF (@Parameter =2 , [Date].[BoundDate])

IIF (@Parameter =3 , [Date].[FullfillmentDate])

Any advice, thanks :)