Create custom Excel 2003 chart data markers

I am trying to customize chart markers conditional on other values in the underlying data table.

Someone else asked a similar question and the solution given was to create a separate data series in the chart for each marker you want different. This solution is workable, but labor intensive.

I thought it might be doable with a VBA macro, setting the color and/or other property(s) of each marker object conditional on other values in the source data table, but I don't know Excel 2003 VBA well enough to figure it out.

Any pointer(s) would be most appreciated!