set variables in Crystal Reports XI

I have a report with several groups:
---> Order Type
----------> Ship Date
---------------->Order Number
---------------------> Model Number
----------------------------Detail Row

i want to use the "Supress if repeated" option on the OrderQty at the detail level, but it also supresses the OrderQty of the previous or next order if the OrderQty is the same.  I only need to supress it if the OrderNumber and Model number repeat.

i have created Global vars in a formula and placed in the Report Header:
global stringvar ProjNum;
global stringvar ModelNum;

Then in the Model Number footer:
Global stringvar ModelNum;
evaluateafter ({@detOrderQty});
ModelNum={order_details.ProductName}

In the Order Number footer:
global stringvar ProjNum;
evaluateafter ({@detModelNum});
ProjNum={Orders.ProjectNumber}

and finally in the Detail Line:
Global stringvar ProjNum;
global stringvar ModelNum;
whilereadingrecords;
if ProjNum={Orders.ProjectNumber}
    and ModelNum={order_details.ProductName} then
0
else
{order_details.Quantity}

My assumption was that the group footers would set the global vars and if the current record didn't match the ProjNum and the ModelNum, they would return the OrderQty, else return 0.

Help is appreciated,
Harold