Mathematical differences between uneven columns?

Hello,

I have four colums in sets of two. I have name and value for day one and the same for day two. Where the name/value combination does not match, I'd like to know the difference (how much the value increased or decreased). Some name/value combinations are on day 1, but not day 2 and vice versa. I need to know which these are, too. How can I accomplish this?

A simple example is attached, although my real data has about 3000 rows at times.

Thanks!