When you enter numbers or formulae on the formula line, you can combine the act of clicking the tick button and selecting an adjacent cell for entry by pressing one of the following keys.
Press Tab. This enters the data and selects the cell to the right.
Press Shift-Tab. This enters the data and selects the cell to the left.
Press the up or down arrow keys. This enters the data and selects the adjacent cell in the direction of the arrow pressed, ie the down arrow selects the cell beneath the current one.