If it is really simply a crosstab with a row field and two summaries, then I would just set this up as a manual crosstab, where you group on item and insert distinctcounts on po# for the total and on a formula for the quarterly number:
if datepart("q",{table.date}) = 1 then //first quarter
{table.po#} else
tonumber({@null})
...where {@null} is a formula that you open and save without entering anything. Remove the tonumber() if po# is a string. Not sure what quarter you are looking for--you could compare the field with, e.g., datepart("q",currentdate).
Then you could just use a group selection formula (report->selection formula->group):
distinctcount({table.po#},{table.item#}) > 2
It is actually sometimes difficult to suppress rows conditionally in inserted crosstabs.
-LB