There *IS* a way to do this for line labels, but it's quite a pain, and it doesn't really work with spanning labels. The trick is to create a couple of "Line" components in your label.
First, set the "Direction Arrow" component so that Visibility is OFF, and the "Fixed length" property is set to "False".
Now create a new "Line" component, and set it so that it draws a line from the Start of the Direction Arrow to the middle of the Direction Arrow. Now hook your "Direction" component to the middle of this line. Create another line that goes from the middle of the Direction Arrow to the End of the Direction Arrow, and hook your "Distance" to the middle of this line.
I've included some pix to help. The image includes three seperate screen shots, showing three different elements. It should help you piece it together. I flagged some of the key settings in red.
It's pretty ugly, and illustrates only one example of how Autodesk really needs to redesign these labels so they aren't so clunky, but it works.
Sinc