There is a way to do this using the Connect command that I think would be much easier, and uses the color scheme.
We just uploaded an example file you can access in DataGraph (File/Online Examples).
The file has one color scheme that is used for the points and the lines.
The approach here is to layer the Points and Connect commands.
In the Connect command, you draw the line segments and add End caps.
Please see the file for details.
Hope that helps!