Reports :: Shading Area Between Two Values In A Chart?

I have show results of scores on a graph but need to show if those scores fall below, in between or above acceptable limits. For example, lets say the acceptable range is between 10.5 and 15.6 but people can scores between 0 and 50. So what I need to do on a report chart/graph is show the actual scores in columns, let access automatically adjust the scale, but have the area between 10.5 and 15.6 on the scale highlighted or coloured or perhaps indicated by two horizontal lines across the chart/graph.