Variable not working as expected in Set

[#1]

Hi All,

I am trying to use the following function:

sum({<weekago={'>52<$(52+$(NumOfWeeks))'}, MONTH_DESC>}CURRENT_SALES)

I want to sum the sales of for weeks in previous year to date time period.

The NumOfWeeks variable is defined as

max({$<YEARAGO={'<1'}, MONTH_DESC>} WEEKAGO)