Define your property as a short.

Insert the typedef enum statement at the begining of the library specification as illustrated:

library SCHEM32Lib
{
   importlib(STDOLE_TLB );
   importlib(STDTYPE_TLB );
   typedef enum
   {
      [helpstring("Diagonal")] Diagonal=0,
      [helpstring("Manhatten")] Rectangular=1,
      [helpstring("Horiz Dogleg")] HDogleg=2,
      [helpstring("Vert Dogleg")] VDogleg=3,
      [helpstring("X Then Y")] XThenY=4,
      [helpstring("Y Then X")] YThenX=5
   }
   LineModeCode;

Now, find the definition of your property in the dispinterface, and change the type from "short" to whatever type you used in your "enum."

dispinterface _DSchem32
{
   properties:
   // NOTE - ClassWizard will maintain property information here.
   // Use extreme caution when editing this section.
   //{{AFX_ODL_PROP(CSchem32Ctrl)
   [id(1)] LineModeCode LineMode;
   [id(2)] short PixelsPerGrid;
   [id(3)] boolean SnapToGrid;
   [id(4)] DrawModeCode DrawMode;
   [id(5)] WireEditCode WireEditMode;