There are several ways to enter a cell range into a formula. Cell ranges and references can be entered into a formula simply by typing in the proper syntax (see Section 6.3 for more details). But manually entering in cell ranges is slow and cumbersome.
When entering data into a cell, and the cursor is at a point where a cell reference is appropriate, it is possible to define a cell reference by selecting a cell via the mouse or keyboard. This selection is a little different from the ordinary selection. It is highlighted by a "marching ants" border.
To make a cell reference using the mouse:
This can be used to select a range of cells just like regular selections.