Can we transform event summary to graph?

I have some problem about event summary. the Orion has shown by list of event as the picture below.

But my customer want to see it as a graph because they want to know how many event occur by time for example if at 15:00 have 100 event then graph is higher than another time and mu customer can click dill-down form graph.

I try to use custom chart but cannot success but I'm keep trying. can you help me some another solution? Pls. >__<