I have defined two calculated measures one called

YTD which is defined against the Foodmart Sales Cubes
Measures dimension as follows:

SUM(YTD([Time].Currentmember),[Measures].[Unit Sales])

and similarly I have defined - Last12Periods as a calculated member
against the Measures dimension in my cube called ProfitCube

SUM(LastPeriods(12),[Measures].[COGS])

I see there is data from the last 36 months in the cube for the Measure
COGS the LastPeriods always returns a value ERR.

The YTD always returns the messages ERR in the cube browser
irrespective whether I select a specific time period or not.

Please clarify what is wrong here how do I get the LastPeriods and the
YTD working

Is there some publication on the web with MDX samples for Lead, Lagm
YTD, MTD and other MDX functions against the FoodMart cube.


Thanks
Karen