Time Intelligence with a Dynamic Parameter?

Hi all, I'm trying to figure out a way to use the DATEADD function or similar while at the same time using a dynamic parameter for the comparison. I want to type in 30 and have it show me an existing measure, but filtered for the last 30 days. I've accomplished that successfully using the measure below (where "X Value" is the parameter):

MEASURE (Last X Days) = CALCULATE( [MEASURE], DATESBETWEEN('Calendar'[Date],

TODAY() - 'Comparison Period'[Comparison Period X Value]+1,TODAY()) )

I'd like to compare to the same period last year using DATEADD. When I try to use CALCULATE with [MEASURE (Last X Days)] as the first argument, and DATEADD for last year as the filter argument, it returns the same result as MEASURE (Last X Days). I suppose I could just subtract 365 from each of the dates above, but I would prefer to use the DATEADD function so I can do the same thing with months, quarters, with changing numbers of days.

Any ideas? Thanks!