adding connection points to UML class diagrams?

[Tim Olsen <tolsen718 gmail com>]

Hello.  I am new to dia and UML, so what I am looking to do here might
not make any sense.

I want to draw a class diagram that looks like this (fixed width font
need here):

         A            B
         |          |   |
         |          |   |
         +----------+   |
         |              |
         |              |
         C            D

Where class C is a subclass of A and B and class D is a subclass of B.
 I would like to have two connection points to the bottom of B so that
the line from D to B does not touch the line from C to B--otherwise it
might look like D is also a subclass of A.

However, there is no option to add a connection point to the class
diagram.  Any recommendations on what I should do?

thanks,
Tim