One of the things we sometimes need to do in Excel is work with values that are sitting in different worksheets. This is exactly the problem shown has right now, where he's been asked to put together a summary of the 2015-2016 sales data. The values are sitting in the 2015 sales sheets. Unlike with anything, there's a good way and there's a not so good way to do this. Let's have a look at something that won't work first. So, I need my 2015 sales total for Aanya. I'm going to come to my sales 2015, click on the sheet, come up to my total, which is over here, and it makes sense to copy paste it. So, I'm going to right-click copy, but you could Control-C as well. Come back to my sales summary, click in the sale and paste, Control-V, or right-click paste. That did not work. Now, the reason it didn't work is because of relative references which we looked at in the previous video. When I have a look at the calculation in the sale, it says add up the four sales to the left of me. Now, coming back to our sales summary, you'll see there aren't four sales to the left, and that's why I'm getting this reference error. So, with formulas, you can't just copy them and necessarily expect to get the right answer. So, what are other options? Well, what some people may think is the obvious choice is to come and actually get that value and just type it in or copy the value in. That is a really bad idea, because if something should update in my sales 2015, this is now going to be incorrect. That's how our workbooks can get out of step and cause us real problems. What we really want to do is somehow pull that value through from sales 2015 sheet. This is actually easier than you might think. Imagine, for example, that I have the value 200 sitting in this sale, and I want whatever sitting in that sale to appear in B4. I come to B4, type equals, click on the sale that contains the value, and enter. That is now pulling my 200 through. If I change this to 600, it pulls that value through. Now, what we want to do is exactly the same, except we want to do it from a different sheet. So, the mechanics are identical. So, I click in B4, type my equals, come to my sales 2015, click on my total, and be very careful, don't try and click back into the worksheet, makes sure you press enter. That work perfectly. Not only that but if the value updates in 2015, this will update. Let's see how to do that again. So, click in C4, type equals, this time I want my sales 2016 total. So, I'm going to come to here, click on it, and again, press enter. That's work beautifully. To get my total, very simple, just use my "AutoSum", and then tab. One thing left to do, and that's our commission. Now, the rates were different for the two years, so we're going to have to actually add up the two commission values. Pretty much the same thing we did before, except we're throwing a little calculation into the mix. I start with my equals, I click into sales 2015, I click on my commission. Now, I have to type my plus. If you have a look in my formula bar here, you can see what I'm doing. Then I come to sales 2016, and I click on my commission. This is the most important part. Do not attempt to click back into summary data. It's like clicking on another sale halfway through a calculation. It will break your calculation. You're finished, you press enter. Now, I'm back in my workbook and my commission has been calculated. Just as we've done in the past, we can select all of those values relative references works even across sheets and I drag it down, and there is my sales summary drawing data from other workbooks. To get my total here, nice little shortcut, I'm going to select all four sales, and click "AutoSum". There's my sales summary complete.