diff --git a/API_GdbModifySurf.cpp b/API_GdbModifySurf.cpp
index efd08dd..73f8b9d 100644
--- a/API_GdbModifySurf.cpp
+++ b/API_GdbModifySurf.cpp
@@ -35,6 +35,34 @@ __stdcall EgtExplodeSurface( int nId, int* pnCount)
    return ExeExplodeSurface( nId, pnCount) ;
 }
 
+//----------------------------------------------------------------------------
+BOOL
+__stdcall EgtSurfFrAdd( int nId1, int nId2)
+{
+   return ( ExeSurfFrAdd( nId1, nId2) ? TRUE : FALSE) ;
+}
+
+//----------------------------------------------------------------------------
+BOOL
+__stdcall EgtSurfFrSubtract( int nId1, int nId2)
+{
+   return ( ExeSurfFrSubtract( nId1, nId2) ? TRUE : FALSE) ;
+}
+
+//----------------------------------------------------------------------------
+BOOL
+__stdcall EgtSurfFrIntersect( int nId1, int nId2)
+{
+   return ( ExeSurfFrIntersect( nId1, nId2) ? TRUE : FALSE) ;
+}
+
+//----------------------------------------------------------------------------
+BOOL
+__stdcall EgtSurfFrOffset( int nId, double dDist, int nType)
+{
+   return ( ExeSurfFrOffset( nId,  dDist, nType) ? TRUE : FALSE) ;
+}
+
 //----------------------------------------------------------------------------
 int
 __stdcall EgtExtractSurfFrChunkLoops( int nId, int nChunk, int nDestGrpId, int* pnCount)