VBA - SUMIFS of multiple worksheets in another workbook

[analysethis]

HI

I've been trying for days and looking through the forums, but i can't figure out how to do it.

I have 2 workbooks. One with the data and one where i want to synthesize the data.

In the second one, i want to do a SUMIFS of the data in the first workbook.
SUMIFS of the values with these conditions:
Same FUND (ex: MFBN0815 but using a variable since it won't always be the same criteria)
Same Serie (ex: Conseiller but using a variable since it won't always be the same criteria)
> or = to Date From
< or = to Date to

I know how to do it if the data is all in the same worksheet (using a SUMIFS formula), but i just can't figure out how to do it if it's in various worksheets (variable number of worksheets).


Example of the fist workbook with the data (there will be many worksheets like this):

FUND	SERIE	DATE	VALUE
MFBN0815	Conseiller	2013/10/01	10 000$
MFBN0815	Conseiller	2013/10/02	10 500$
MFBN0815	Investisseur	2013/10/01	20 000$
MFBN0817	Conseiller	2013/10/01	50 000$

<tbody>
</tbody>

Example of the second workbook where i want to synthesize the data:

FUND	SERIE	DATE FROM	DATE TO	SUMIFS
MFBN0815	Conseiller	2013/09/25	2013/10/02	??????

<tbody>
</tbody>

Any idea?

Thank you