Doing LFL Calculations

I'm a bit stuck...

I'm trying to do a LFL measure based on week/month/quarter/year using a 4-4-5 custom calendar. I need it at location level, but obviously, I want to aggregate it up to site,region level. Every time I aggregate the measures I have created they forget it is supposed to be at location level and the LFL calc gets aggregated to site or region. Measures work on the fly so it isn't surprising, however, is there another way to do LFL?