You may be able to get that look by typing a value and hitting alt-enter (to
force a new line within the cell) (and then add some spaces to the top or bottom
depending on the direction of the diagonal).
Format|Cells|border tab is where you could draw the diagonal.
But once you do this, it may look nice(?), but it'll become really awful to
extract stuff you need for other formulas. (I wouldn't do it.)
