I have looked at the docs but don't see anything obvious. This is pretty fundamental of a thing to do so I am thinking that I am missing it. I currently need to determine if a face is coplanar with the front plane. I know later that I will need other mate-like and sketch relationship as well. 

I do see the ISketchRelationshipManager but I am guessing that this will return no possible relationships since neither are a sketch entity.

I also see the IMeasure. I *could* use it to determine if the face and plane is parallel and intersecting. This method just seems a little bit of a round about way to determine this.

Is there a better way to determine what I am after here?