Generate relationships from list

Hi,

This is a bit complicated to me, and I don't know if this is a standard problem in mathematics or other discipline that has a ready-made solution so I thought I would get some advise before embarking on a coding mission that may or may not work.

The data looks like this:

Column A
Group
A, B
B, C
C, D
A, C
B, D
A, D

In column B, I would like to know the relationship between the individual letters. For example:

Column A....... Column B
Group............Relationship
A, B................1st level
B, C................1st level
C, D................1st level
A, C................2nd level
B, D................2nd level
A, D................3rd level

Graphically it would look something like this:

Relationships.jpg

Any thoughts, ideas or suggestions are welcomed.

Thanks.

abousetta