If you have more than one criteria then you can't use SUMIF - use
SUMPRODUCT instead. If you are using XL2003 or earlier then you can't
use full-column references with SP, and it is better to keep the
ranges just as large as required to cover your data. Something like
this:
=SUMPRODUCT(--(A1:A100="Apple"),--(B1:B100>=50%),C1:C100)
The -- converts True and False to 1 and 0 respectively for each
element. Another way of writing it is:
=SUMPRODUCT((A1:A100="Apple")*(B1:B100>=50%),C1:C100)
or even:
=SUMPRODUCT((A1:A100="Apple")*(B1:B100>=50%)*(C1:C100))
where * is equivalent to AND.
Hope this helps.
Pete