Hi Paul,
Use this code in the selection formula:
cdate(Picture(totext({Number Field},'#'), 'xxxx/xx/xx')) IN
DateAdd('ww',-52,cdate(Picture(totext(x,'#'), 'xxxx/xx/xx'))) TO DateAdd('ww',-54,cdate(Picture(totext(x,'#'), 'xxxx/xx/xx')))
If you wish to go back 360 days, you can use:
cdate(Picture(totext({Number Field},'#'), 'xxxx/xx/xx')) IN
DateAdd('d',-360,cdate(Picture(totext(x,'#'), 'xxxx/xx/xx'))) TO DateAdd('d',-380,cdate(Picture(totext(x,'#'), 'xxxx/xx/xx')))
-Abhilash