Hi,
Try this:
declare @yesterday datetime
declare @today datetime
set @yesterday = convert(datetime,convert(varchar(11),dateadd(dd,-1,getdate()),106) + ' 15:00:00.000')
set @today = convert(datetime,convert(varchar(11),getdate(),106) + ' 08:00:00.000')
SELECT PONum
FROM PO
WHERE
POStatusDate > @yesterday AND POStatusDate < @today
Hope that helps,