How can I get the mirror plane of a mirrored part

Hi

I have a part opened in SolidWorks. This part has an externalmirror reference to another part.

My question is: How can I get the plane which was used to mirrorthe reference part?

I only managed to get the path to the original part using this C#code:

ModelDoc2 modelDoc = m_appSolidWorks.ActiveDoc as ModelDoc2;
PartDoc part = modelDoc as PartDoc;
string originalPartPath = modelDoc.GetExternalReferenceName();

Any help will be appreciated.
Thanks
AdarSolidworksApi macros