The F4 function key has a dual personality. When used normally it will repeat your last action. This is useful for formatting, deleting rows and other operations that require a few keystrokes. Pressing F4 can reduce the keystrokes.

Its other use is to add $ signs to cell references when editing in the formula bar or within a cell. Pressing F4 while editing in the formula bar (Excel displays 'Edit' in the bottom left-hand corner of the screen) when the cursor is next to or in a cell reference will insert $ signs to the cell reference. Eg. A1 turns into $A$1. This is a fixed reference, which will not change when you copy the formula to other cells.

As you keep pressing F4 the $ signs will move around. The sequence is $A$1, A$1, $A1 and back to A1. The second and third in the sequence are mixed references as they fix the row and column respectively.

The normal A1 reference is a relative reference, it changes relative to the where you paste it.

You can remember the F4 key adds the $ signs by looking at the 4 key as it has the $ above it.  

Neale Blackwood a senior business analyst with Access Analytic Solutions, which provides financial modelling, management reporting services, as well as advanced Excel training. You can email Neale at nblackwood@accessanalytic.com.au.