Do you want to set a (comma separated) list of year values to a variable or use a certain period (last 7 years) for limiting the display / calculation of a dimension / expression?
From your post, I would assume the first; is Current year another variable /selection or do you want to use the current timestamp?
If you want the latter, I would use set analysis and limit for example dimension Year to the last 7 years.
e.g. sum( {$<Year = {">= $(=year(now())-8) <= $(=year(now())-1)"}>} Sales )
[Be aware that you might need to set other time dimensions to empty selection if needed within the set, depending your data model]
(Besides I think the last seven year for current year 2012 should be 2011 to 2005, right?)
