Unfortunately, you can't use the simple approach I posted since it is a calculated field.
You would need to use Sastry's approach to show the counts on the Group Footer. I would change his second formula to:
EvaluateAfter({@formula_for_po_backorders});
Numbervar sum;
If {@formula_for_po_backorders} > 0 then
sum := sum + 1
Replace {@formula_for_po_backorders} in the above code with the formula name for PO Backorder.
-Abhilash
