Automatic midpoints?
 

I'm working on a network diagram that needs many parallel connections between two devices. The connections are shown as lines, but they need to be separated from each other. I've done a few drawings by adding a midpoint to the lines, making them curves and adjusting the distance between the lines, but I would like a way to make sure the midpoint is at the exact center of the line and the distance between midpoints on each line is excatly the same. Is there any way to have OmniGraffle (pro) automatically place a midpoint at the exact center of a line?

Example attached.