How to fill random cells with values
To fill multiple cells with the same value, hold down the “CTRL” key while marking the cells that you want to fill. Here I’ll mark the cell for February and then mark a cell each quarter. Release “CTRL” and enter the amount you want to fill the cells with. Here I’ll write 1200. Press “CTRL” again and press “Enter”. All the cells that were marked are filled with the value.
To fill multiple, random cells with zero, type 0 in one of the empty cells. Right-click and copy. Then mark the entire data range with empty cells that you want to fill, click “Paste” and select “Paste Special”. Under “Operation” click “Add” and then “OK”. There, now zero has been added to all cells.