How do I add an average button in calc?

I cannot see how I can add an “average” button in Calc. I can see the “sum” button, but would like an average button also. Is this possible ?

I like the sum button because it automatically selects the rows above. If I need another function, such as the mean, I still use the button and change the formula, e.g. from something like SUM(A1:A2) to AVERAGE(A1:A2).

Sure. You can record a macro and assign a button to it