Conditional formatting colour scale-Include only cells containing value greater than 0

I have 5 different cells that return totals. At any point, as little as 2 of the 5 may have value and up to all 5. However when a colour scale is set to show highs and lows, it includes all cells including the empty ones. Excel thinks these values are 0 and include them in the scale. So the actual low number is coloured yellow rather than the green it should be. I want to only include values that are greater than zero in the colour scale.