Year to date to week - Index Match & Sum Ifs function?

[Jonas0]

Hello Everyone!

I struggled with setting up a formula, that shows the sum of the year to date numbers of the past and current month.
In the current month it should be possible to differentiate until which week the sum should be drawn.
My guts tell me that a combination of a Index Match function and Sum if function could be the solution, but I could not find the right way..

To make the situation a bit clearer:

[TABLE="width: 500"]
<tbody>[TR]
[TD]Country[/TD]
[TD]Week 1[/TD]
[TD]Week 2[/TD]
[TD]Week 3[/TD]
[/TR]
[TR]
[TD]China[/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[/TR]
</tbody>[/TABLE]

[TABLE="width: 500"]
<tbody>[TR]
[TD]Country
[/TD]
[TD]Week
[/TD]
[TD]Jan
[/TD]
[TD]Feb
[/TD]
[TD]Mar
[/TD]
[/TR]
[TR]
[TD]China
[/TD]
[TD]Week 1
[/TD]
[TD]1000
[/TD]
[TD]2000
[/TD]
[TD]400
[/TD]
[/TR]
[TR]
[TD]China
[/TD]
[TD]Week 2
[/TD]
[TD]400
[/TD]
[TD]750
[/TD]
[TD]700
[/TD]
[/TR]
[TR]
[TD]China
[/TD]
[TD]Week 3
[/TD]
[TD]1200
[/TD]
[TD]3000
[/TD]
[TD]2100
[/TD]
[/TR]
[TR]
[TD]China
[/TD]
[TD]Week 4
[/TD]
[TD]800
[/TD]
[TD]1200
[/TD]
[TD]300
[/TD]
[/TR]
</tbody>[/TABLE]

Assuming that it is the 2. week of February, below 'Week 2' in the first table the sum of January and Week 1 & 2 of February should be displayed.

Does anyone have an idea?

I'd be very grateful for any advice.

 

[Jonas0]

I forgot to mention: The second table is the 'data base' and the first table is the 'out put table'