Select in field search string issue

[#1]

Hi All,

I am trying to select the last two weeks by default in multibox. I am writing the following string in search string

='('& date(max([Weekending Date])-7) &'|'& max([Weekending Date]) &')'

If I type only date(max([Weekending Date])-7) or max([Weekending Date]) then it selects  values (09-09-2012 or 16-09-2012) . However If I try to enter both values as in the above string

='('& date(max([Weekending Date])-7) &'|'& max([Weekending Date]) &')'

It is selecting 09-09-2012 and 02-09-2012

Can someone guide me what mistake am I making in the above string

Regards

Arif

[chematos]

='('& date(max([Weekending Date])-7) &'|'& date(max([Weekending Date])) &')'

I 've used this expression in an object box and is working fine for my dates