We only charge for a meal tray served if the number is over three per month;
if they only get three, no charge, if they get four, we charge for one, five,
we charge for two and so on.

Is there a formula that will provide the following:

If the sum of the preceeding three cells (totalling the number of breakfast,
lunch and dinner trays) is = or < 3, I need it to return 0; however, if the
number is greater than 3, I need it to return the actual number minus 3.

Any help?