[VBA] Calculate how often does two person appear at the same time

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Attached below is a sample data.
The purpose is to create a table (shown below) which summarizes how often do two persons occur at the same time.

E.g.
Use "Rebecca" as an example.
Total count of "Rebeceaa" occurence in all invoices = 4.
For invoice number 4, "Wendy" and "Mary" also exist at the same time with "Rebecca".
So their occurrence frequency relative to "Rebecca" would be 1/4 (25%) and 1/4 (25%) respectively.

I would like to automate the above process ( fill-up the whole table ) via vba or any other way convenient and fast.
I get a large data set, >1000 data row. Manual calculation would be deadly.
Hope someone can help.

Excel 2012
	A	B	C	D	E	F	G	H	I	J	K	L	M
1	Invoice	Name		Total Count
2	1	Rebecca		Betty	4
3	4	Wendy		Ken	1
4	4	Rebecca		Mary	3
5	4	Mary		Philip	2
6	5	Mary		Rebecca	4
7	10	Betty		Susan	1
8	10	Betty		Thomas	2
9	10	Betty		Tom	1
10	22	Philip		Wendy	1
11	24	Rebecca
12	26	Betty		Simultaneous Occurrence for same invoice (= ccurrence / total count )
13	28	Tom			Betty	Ken	Mary	Philip	Rebecca	Susan	Thomas	Tom	Wendy
14	28	Susan		Betty
15	29	Thomas		Ken
16	30	Thomas		Mary
17	30	Philip		Philip
18	36	Ken		Rebecca			25%		100%				25%
19	37	Mary		Susan
20	41	Rebecca		Thomas
21				Tom
22				Wendy
工作表3

Thanks a lot!