What are the conditions?
=SUMPRODUCT(--(A1:A5>5),--(B1:B5<6),C1:C5)
in cell c6. In this case it totals the cells in C1:C5 as long as the
corresponding cell in columns A and B meet the folowing conditions:
The value in column A should be greater than 5
The value in column B should be less than 6