In this how to video, you will learn how to create a diagonal sum in Microsoft Excel 2007. First, open the program and make a large selection. Type in =int(rand()*500) and then press control enter. This will create random numbers for the cells in the selection. From here, click conditional formatting and select new rule. From here, type in =column(A1)-row(A1)=$H$1. For the format, choose a contrasting look, such as a purple background and bold numbers. Click okay. If you type -1 or -2 in this column, it will move the purple diagonal background up or down the selection of numbers. Next, in a blank cell type in =sum((column(A1:E5)-row(A1:E5)=H1)*AI:E5) and then press control shift and enter. You will get the sum of these diagonal numbers.