diff --git a/EGkVolZmap.h b/EGkVolZmap.h
index 8dc430a..911a338 100644
--- a/EGkVolZmap.h
+++ b/EGkVolZmap.h
@@ -31,8 +31,9 @@ class __declspec( novtable) IVolZmap : public IGeoObj
       virtual bool CreateFromFlatRegion( const ISurfFlatRegion& Surf, double dDimZ, double dPrec, bool bTriDex) = 0 ;
       virtual bool CreateFromTriMesh( const ISurfTriMesh& Surf, double dPrec, bool bTriDex) = 0 ;
       virtual bool GetAllTriangles( TRIA3DLIST& lstTria) const = 0 ;
-      virtual bool GetBlockTriangles( int nBlock, TRIA3DLIST& lstTria) const = 0 ;
+      virtual int  GetBlockCount( void) const = 0 ;
       virtual bool GetBlockInfo( std::vector<bool> & bModified) const = 0 ;
+      virtual bool GetBlockTriangles( int nBlock, TRIA3DLIST& lstTria) const = 0 ;
       virtual bool GetDexelLines( int nDir, int nPos1, int nPos2, POLYLINELIST& lstPL) const = 0 ;
       virtual bool SetTolerances( double dLinTol, double dAngTolDeg = 90) = 0 ;
       virtual bool SetStdTool( const std::string& pToolName, double dH, double dR, double dCornR) = 0 ;