I am trying to sum a customers sales for a year to date value so I can
compare it with the year to date sales for the previous years. The formula is:

=SUMPRODUCT(--('Wholesale Orders'!G2:G2008<=TODAY()),--('Wholesale
Orders'!G2:G2008DATE(2007,12,31)),--('Wholesale
Orders'!C2:C2000)=A5,--('Wholesale Orders'!F2:F2008))

It works perfectly until it calculates array #3, cell #A5 of the current
worksheet is a text value (customer name).