CR v.10

I have a subreport with a slight problem. I don't think the problem is related to this report being a subreport.

I have three tables linked in the following sequence using Inner Joins, Not Enforced, Link Type is Equal between the tables.

Inventory Table 1 with ITEM_NUMB field
PO Number Table with ITEM_NUMB field
Inventory Table 2 with ITEM_NUMB field

I link all 3 tables together on ITEM_NUMB field.
I am getting the report I want and more. I want to exclude all records from the report where Inventory Table 2 has a record that matches Inventory Table 1 on ITEM_NUMB and PO Number Table on ITEM_NUMB.

It's not working. I don't know what I am doing wrong. I tried excluding the records using Database Links and changing the Join and Link Type. I tried adding a Record Selection formula. And I tried using a Group Suppression formula in the Group Section of the report, but no matter what I have tried it has not given me the report results that I had desired.

This is my current Group Section Suppression formula and I was simply going to add onto it for the final Suppression conditional, but I keep getting the reverse of what I want when I add onto it. See add on code following the current good, working code.

// This code works, but gives me more records than I had wanted.
// So I added more code to Suppress more records from printing
// as shown in the second set of code below.
WhilePrintingRecords;
(Left({IN10.ITEM_NUMB},2)<>"SH" and
Left({IN10.ITEM_NUMB},2)<>"HW" and
Left({IN10.ITEM_NUMB},2)<>"FW") or
{@grp_po}=""

// This code gives me the reverse of the records I had wanted
// no matter how many ways I tried.
WhilePrintingRecords;
(Left({IN10.ITEM_NUMB},2)<>"SH" and
Left({IN10.ITEM_NUMB},2)<>"HW" and
Left({IN10.ITEM_NUMB},2)<>"FW") or
({@grp_po}="") and
({IN10.ITEM_NUMB})={IN42.ITEM_NUMB} and
{IN10.ITEM_NUMB}={PO11.ITEM_NUMB})

I was able to get the reverse of what I wanted in the report using Group Section Suppression formula, but was unable to get the inverse of the reverse, if you know what I mean.

Please let me know what I am doing wrong? It seems simple enough, but I am missing something somewhere. Thanks ahead of time for your help.