Fixing size and shape of Diagram Objects

[trickster60]

I am writing an Add-In and I want to create "part" like elements in that they behave like "parts" in diagrams, ie when they are embedded within another element they cannot be dragged out of the owning element. However I also want them to behave a bit like "ports" in that their shape and size cannot be altered. Can anyone help me?

I have scoured the documentation on how this might be done without success. I was wondering if Element.CustomProperties for Ports or Parts might be a means of achieving this but I have not been able to find any specific information on the CustomProperties of the various types of elements.

Thanks in advance