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!

If you put the following formula in F2 and copy down does that meet your needs?

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Thanks, but it's not perfect. What this doesn't do is calculate differences when the name/value are both there, but not lined up, like the change in g. Can we also make the differences always be day 2 minus day 1?

Thanks again.