So I spend 3 months building the most beautiful spreadsheets in the history
of humanity, then a user goes and breaks it. Here's the problem - it's about
deleting rows when you have a SUMPRODUCTs that span multiple sheets. on
those named ranges go all N/A

Let's say I have a SUMPRODUCT that spans different sheets

=SUMPRODUCT((Sheet1!C1:C10)*(Sheet2!C1:C10))


Now here's the rub : Let's say a user deletes row 5 in Sheet1. The
sumproduct then adjusts itself to

=SUMPRODUCT((Sheet1!C1:C9)*(Sheet2!C1:C10))

And proceeds to go the shape of a pear, giving out only a solitary splutter
of N/A.

Any suggestions for how I can avoid this? All I can think of is not allowing
the deletion of rows by protecting sheets...