Index match lookup multiple column & row headers and sum

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Hi

I have the following table with dates down the rows which is split into 5 activities and the columns are split between 5 desks with a person at that desk:

	A	B	C	D	E	F	G
1			Desk 1	Desk 2	Desk3	Desk 4	Desk 5
2	Date	Activity	Bob	Julie	Derek	John	Debbie
3	01/01/2018	A	10		10	10
4		B		10		10
5		C	10		10	10	10
6		D		10
7		E		10	10		10
8	Date	Activity	Derek	Bob	Debbie	Julie	John
9	02/01/2018	A			10		10
10		B	10		10	10
11		C	10	10		10
12		D			10		10
13		E		10		10
14	Date	Activity	Debbie	Derek	Bob	John	Julie
15	03/01/2018	A	10		10		10
16		B		10		10
17		C		10	10
18		D			10		10
19		E	10			10
20	Date	Activity	Bob	Debbie	Derek	Julie	John
21	10/02/2018	A			10	10
22		B		10		10	10
23		C			10		10
24		D	10	10		10
25		E	10		10		10
26	Date	Activity	John	Julie	Debbie	Derek	Bob
27	05/03/2018	A	10			10	10
28		B			10
29		C	10		10
30		D		10		10
31		E				10

<colgroup><col style="width: 25pxpx"><col><col><col><col><col><col><col></colgroup><thead>
</thead><tbody>
</tbody>

Sheet1​

Now, on any specific day any one of those people could sit at any of the desks but the activities remain the same.

What I want is a summary sheet that sums all activities per person by month:

	A	B	C	D	E	F	G
1	Month	Activity	Bob	Julie	Derek	John	Debbie
2	January	A	20	10	10	20	20
3		B		20	20	20	10
4		C	30	10	30	10	10
5		D	10	20		10	10
6		E	10	20	10	10	20
7	February	A		10	10
8		B		10		10	10
9		C			10	10
10		D	10	10			10
11		E	10		10	10
12	March	A	10		10	10
13		B					10
14		C				10	10
15		D		10	10
16		E			10

<colgroup><col style="width: 25pxpx"><col><col><col><col><col><col><col></colgroup><thead>
</thead><tbody>
</tbody>

Sheet2​

Is this possible using formulas in each of the cells in Sheet 2 or does it need VBA?

Thanks