On your SharePoint site, you want people to enter values for cell B4 (price) and for cell B5 (number of units to be sold). To do this, Excel Services requires that these cells be named. Why? As you'll see later on, instead of typing directly in these cells, people will type values in a special pane next to the worksheet. The names for cells B4 and B5 will help people know what to do and where to type in the pane.
First, make sure these cells don't already have names. In Excel, click first in cell B4 and then in cell B5, and look for names in the Name Box on the Formula Bar. In the picture, only the cell address B4 is in the Name Box, so the cell needs to be named.