Sumif Accross Multiple worksheets

Hello,

I have multiple projects worksheets and various employees work on more then one project. I want to sum their weekly hours by various projects into the worksheet called "Consolidated worksheet".

In the attached spreadsheet - if I need to calculate total hours for week 10 Feb 14 in cell F12 - by adding all worksheets highlighted in green - which matches employee in cell C12 of "consolidated worksheet" - how I do this??

If you need any clarification - please let me know.

Thanks.

Harry.