>In what context do you need to globally query to get an invoice total? Do you store the invoice total in the invoice header?

In most cases, a printed report where I want multiple invoice totals in a row.

>If necessary, you can save the current work area and set it back within the function. Calling this function would probably less efficient than the case where you already have the line items loaded for the current invoice.

If I have unsaved changes, loading the data in a separate cursor won't give the correct results. And if I always reload the current cursor, I've lost those changes. Sergey's suggestion seems... too simple, but I'll give it a try.