You could add a field to Customers that holds the last date an order was placed.  Tha field can be updated automatically with XPOST command from new orders.  Then you can retrieve all Customer records where LastOrderDate is over 6 months.

You could do this now with existing data:
Add the Read Only element LastOrderDate to Customers, bound to a date field.
Add programming to Orders to do the XPOST for all new orders from this point on.
Retrieve all Orders, Sort by Dates in Ascending order.
Do a Mass Update from these Orders records.
Mass Update to do XPOST from Orders to Customers, posting the order date to that LastOrderDate.

That will update all the Customer records, in date order, so the most recent order date will be the value.
Now you can retrieve all those customers with no orders in last 6 months.

Can also use a similar technique to keep a running total of YTD Sales by posting the Order total to a similar YTDSales, ReadOnly, currency element in Customers.

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You could also do some programming to calculate Orders Totals within a date range on demand with a button, or something that updates every time you open a Cusotmer records, but this eliminates the programming, and should be faster since no calculations need to be processed.  Info is real time, available to seach with any date ranges.....

Bob,

Thanks again for your quick reply.  I've been able to add the XPOST command for all new orders, but I'm confused about the Mass Update to XPOST.  I've done the search and the sort, so I have all orders shown with ascending order dates.  Am I to simply insert my XPOST command into the order date section of the Mass Update Program Editor Box?  Sorry, I'm a nervous nelly and not totally sure on this step, though it is exactly what I need to do.

I appreciate your help on this!

Congratulations, well done miss_doo. 

Hope it did what you wanted.