Net movement between categories

[DickyMoo]

Hi All,

I am tracking movement of members between categories, "Affiliate", "Fellow" etc.

Members can move both ways between these categories, e.g. from Affiliate to Fellow, and from Fellow to Affiliate. (Note, if that sounds odd, its just an illustration).

Does anyone have any ideas on how I can show the net movement?

So if:
10 go Affiliate to Fellow is +10
7 go Fellow to Affiliate is -7
Net Affiliate to Fellow is +3.

Should I set up a table with the combinations of all Prior and Current categories and allocate + or - to each?

Any suggestions?

Thanks
Rich