Displaying an Average Value in a Scatter Plot as own Data Series

Hi,

I am using a scatter plot to show how my data samples are distributed. No problem until this point. I would like to show in my scatter plot the samples average and attach something like whiskers to it to show the standard dev. My first idea was adding a new data series, putting it at the location the mean is and attach whiskers expressing the standard dev. That works - but it is irritating, a sample point is forced to use one of those predefined icons for sample points (the little triangle, square, etc.).
People who look at it think of my mean as an own data point that is different from everything around it. It is not perceived as the average. It is really confusing so I am looking for a way to alter a sample points appearance that it no longer looks like a sample point, but something 'different'.
Is that somehow possible? The ugly hack would be to draw a shape over my chart and hope that I never accidentally move it while working in the chart (unprofessional solution).

I was thinking about a box plot and copying the box-shape over into my chart, but that did not work. I guess I ask for too much drag & drop magic here.

Anyone any ideas how to present a mean in a scatter plot?