Excel SUmif formula over several worksheets

I have a workbook with numerous worksheets which I have inherited.

What I need to do it total the contents of all the cells H9 if cell b3 is less than 30 days old.

I know that I can's use SUMIF or even IF but surely there is a formula that says if cell B3 on each of the sheets is less than 30 days ago, include the contents of cell H9 in a total.

The workbook has a blank sheet called First at the beginning and last at the end which envelops all of the worksheets.

Thank you