A Problem about Legend in Designing Crystal Reports Chart

Hi, everyone, I'm here again.

I'm designing a chart in CR designer. As is shown below.

When I print the chart with color, it is perfect.

But when I print with only black and white, it is hardly to recognize which is C1, which is C2, which is C3..........

So I want the legend show different shapes, for example, C1 --  round, C2 -- rectangle, C3 -- star.........

like the below picture.

Legend I want

So, how can I do to accomplish it.

Thanks.