diff --git a/EGkVolZmap.h b/EGkVolZmap.h
index 0366288..f56f96a 100644
--- a/EGkVolZmap.h
+++ b/EGkVolZmap.h
@@ -29,10 +29,10 @@ class __declspec( novtable) IVolZmap : public IGeoObj
    public :
       virtual bool CopyFrom( const IGeoObj* pGObjSrc) = 0 ;
       virtual bool Clear( void) = 0 ;
-      virtual bool Create( const Point3d& ptO, double dDimX, double dDimY, double dDimZ, double dStep, bool bTriDex) = 0 ;
-      virtual bool CreateEmpty( const Point3d& ptO, double dDimX, double dDimY, double dDimZ, double dStep, bool bTriDex) = 0 ;
-      virtual bool CreateFromFlatRegion( const ISurfFlatRegion& Surf, double dDimZ, double dStep, bool bTriDex) = 0 ;
-      virtual bool CreateFromTriMesh( const ISurfTriMesh& Surf, double dStep, bool bTriDex, double dExtraBox = 0) = 0 ;
+      virtual bool Create( const Point3d& ptO, double dDimX, double dDimY, double dDimZ, double dStep, bool bTriDex, int* nError = nullptr) = 0 ;
+      virtual bool CreateEmpty( const Point3d& ptO, double dDimX, double dDimY, double dDimZ, double dStep, bool bTriDex, int* nError = nullptr) = 0 ;
+      virtual bool CreateFromFlatRegion( const ISurfFlatRegion& Surf, double dDimZ, double dStep, bool bTriDex, int* nError = nullptr) = 0 ;
+      virtual bool CreateFromTriMesh( const ISurfTriMesh& Surf, double dStep, bool bTriDex, double dExtraBox = 0, int* nError = nullptr) = 0 ;
       virtual int  GetBlockCount( void) const = 0 ;
       virtual int  GetBlockUpdatingCounter( int nBlock) const = 0 ;
       virtual bool GetBlockTriangles( int nBlock, TRIA3DEXVECTOR& vTria) const = 0 ;