That would depend on what LEVEL of Pcdmis you have (NOT version!). The 'basic' level does NOT have an elipse, the full 'level' (CAD++) has it as an AUTO FEATURE (CTRL-F)
I'm wondering if you could measure it as a circle. Use the minor diameter as the circle's diameter and set a large enough check distance that it will hit the major diameter.
We only have the basic version. I think I need to talk the company into getting the cad++. It has some other nice features. I will try to satisfy what I need with the minor dia. Thanks! Jeff