need to show only currents 12 weeks from 52 weeks

[#1]

hi all,

can anyone help me

i am having 52 weeks in this i need to show only current 12 weeks in list box how can i exclude 40 weeks from the 52 weeks

i am using this expression but it is not working

=IF(Num(Week) >= (Max({1}Week) - (12*7)),Week )

thanks in advance