SUMIF with Multiple IF Criteria

HELP

I need a formula to help me analyse a particurlarly large spreadsheet!

I need to count the items that match multiple criteria (i.e. Region Code equal to 1 and Percentage up to 40%) and then get the total value of those cases.

I have this formula which counts the items:
=SUM((A2:A2000=1)*(B2:B2000<=0.4))

What I need is something that will then SUM the value of the cases (in Column C) that match the specified criteria.

I've tried using SUMIF with the formula above as the criteria, but keep getting the "Formula contains an error" message.

Any assistance greatly appreciated.

JAF