For this lesson, we need to open the sample file: First Quarter Sales and Profit-9, from your Sample Files folder. AutoFill can save you a lot of time when extending or copying text and number ranges. But the story's not over yet, because AutoFill can also work with formulas. AutoFill's ability to copy and adjust formulas is one of the most powerful tools in Excel's impressive armory. Consider the formula in cell: B9. I'll click on cell: B9, and then I can see the formula in the top Formula bar. It's: =SUM(B4:B8), because it's adding up all of the sales figures for January. Now, consider what would be the correct formula in cell: C9. It would be: =SUM(C4:C8), for February sales. And for cell: D9, it would be: =SUM(D4:D8). Let's now have a look at what the correct formulas would be for each column. You can see that, as we move to the right, the letter part of any cell references needs to be incremented. So, as we move to the right, B becomes C, becomes D. And AutoFill is clever enough to know this. So when you AutoFill a formula, this is exactly what AutoFill will do automatically for you. Now we're back to normal again, let's AutoFill the formula in cell: B9, to cells: C9 to D9. So I click in cell: B9, hover the mouse cursor over the AutoFill button on the bottom right-hand corner of the cell. I make sure I see the Black Cross cursor shape, and then drag two cells to the right. Now, you might think that something's gone wrong here, because February sales are exactly the same as January sales. In fact, this is completely correct. Coincidentally, the numbers add up to 129,000 in both cases. But let's audit the formulas now, to make sure AutoFill has done its job correctly. So I click on cell: B9, and look at the formula in the top Formula bar: =SUM(B4:B8). I now move to the right: =SUM(C4:C8); that's correct. And to the right again: =SUM(D4:D8), and that's correct, for March. So you can see that AutoFill has done a wonderful job in adjusting the cell references within the formulas. But now let's consider the Average sales in cell: E4. This time, it's: =AVERAGE(B4:D4). If we were to consider the average for Los Angeles, it would be: =AVERAGE(B5:D5). And, as we move down the list, it would be: =AVERAGE(B5:D5), =AVERAGE(B6:D6), =AVERAGE(B7:D7), =AVERAGE(B8:D8), =AVERAGE(B9:D9). So, as we move downwards, it would seem that we need to increment the number part of the formula instead of the letter part of the formula. Let's see if AutoFill is clever enough to do this for us. I hover the mouse cursor over the AutoFill button at the bottom-right corner of the cell, and then drag down to the bottom. And you can see that AutoFill seems to have done its job well again. Let's audit the formulas. In cell: E4, we have: =AVERAGE(B4:D4). The next cell, it's: =AVERAGE(B5:D5), =AVERAGE(B6:D6), seven, eight, nine. So, once again, AutoFill's delivered, by correctly adjusting the cell references in the formulas. If we look at the MAX formula in cell: F4, we can see another candidate for AutoFill: =MAX(B4:D4). Let's AutoFill this down to the bottom, and make sure that AutoFill has given us the correct answers again. The maximum sales for Los Angeles was 43,000. That's correct, in March. For London: 22,000, also in March. 35,000 for Paris, that is the biggest value, in January. 15,000, that would be February, for Munich. So AutoFill has given us the correct formulas once again. In the next two lessons you'll discover some even more amazing things you can do with AutoFill. And in Session 3, we'll really take AutoFill to the max. But all that's left to do in this lesson is to save your work. And this time, let's save it as: First Quarter Sales and Profit-10. And, as usual, I'll save it to the folder above my Sample Files folder. I click the Save button and you've completed Lesson 2-15: Use AutoFill to adjust formulas.