Sum the difference in amounts if items are in two tables

[steinfm]

I have two tables that have data. One has estimated amounts and one has actual amounts. So, suppose I have a person (Steve) that we anticipate will buy oranges for $4 (Worksheet 1), but he actually buys the oranges for $5 (worksheet 2). The difference is $1. What I want to do is to add up all of the differences between worksheet 1 and worksheet 2, but only when the person on worksheet 2 matches worksheet 1. By that I mean, if we have Oscar on worksheet 1, but not on worksheet 2, we don't need to worry about him. To add to this, I also only want to add the difference if the currency is a certain currency (USD). I'm attaching a file so you can see.

Can someone help me with the right formula? I'm thinking sumproduct will work, but I don't understand that formula enough to make it work.