diff --git a/EGkSurfFlatRegion.h b/EGkSurfFlatRegion.h
index a7119e9..3c823ff 100644
--- a/EGkSurfFlatRegion.h
+++ b/EGkSurfFlatRegion.h
@@ -34,6 +34,7 @@ class __declspec( novtable) ISurfFlatRegion : public ISurf
       virtual bool Subtract( const ISurfFlatRegion& Other) = 0 ;
       virtual bool Intersect( const ISurfFlatRegion& Other) = 0 ;
       virtual bool Offset( double dDist, int nType) = 0 ;
+      virtual bool GetGrossArea( double& dArea) const = 0 ;
       virtual const Point3d& GetPlanePoint( void) const = 0 ;
       virtual const Vector3d& GetNormVersor( void) const = 0 ;
       virtual int  GetChunkCount( void) const = 0 ;
diff --git a/EXeExecutor.h b/EXeExecutor.h
index b9b4d4c..3e9b6e1 100644
--- a/EXeExecutor.h
+++ b/EXeExecutor.h
@@ -541,6 +541,7 @@ EXE_EXPORT bool ExeCurveCompoCenter( int nId, int nSimpCrv, int nRefId, Point3d&
 EXE_EXPORT bool ExeSurfArea( int nId, double& dArea) ;
 EXE_EXPORT bool ExeSurfVolume( int nId, double& dVol) ;
 EXE_EXPORT bool ExeSurfFrNormVersor( int nId, int nRefId, Vector3d& vtNorm) ;
+EXE_EXPORT bool ExeSurfFrGrossArea( int nId, double& dArea) ;
 EXE_EXPORT int  ExeSurfFrChunkCount( int nId) ;
 EXE_EXPORT int  ExeSurfFrChunkSimpleClassify( int nId1, int nChunk1, int nId2, int nChunk2) ;
 EXE_EXPORT int  ExeSurfTmFacetCount( int nId) ;