Sumproduct weighted average

[CROY1985]

Hi all

I need to push feed some weighting into the formula below:

=SUMPRODUCT(--('[Weather Archive.xlsx]Reports'!$A:$A>=C4)*('[Weather Archive.xlsx]Reports'!$A:$A<=D4),'[Weather Archive.xlsx]Reports'!$C:$C)

My weightings are in the sheet 'regionalweighting', Column A has Region (North, South, East, West), Column B has the weighting (10%, 30%, 45%, 15%)
In terms of '[Weather Archive.xlsx]Reports', the regions are listed in column B

I would rather calculate the weightings in formula than having a calculation column added to '[Weather Archive.xlsx]Reports'.

Is this possible?

Thanks

Chris