How to create shared cell definition from drawing file content

I need help to create a shared cell definition using the content in a drawing file. The drawing file is a dwg and contains 3D data.

I have used the following code (some parts omitted) and it creates a definition but it does not have any valid content. The file opens ok and all functions return SUCCESS.

...

mdlWorkDgn_openFile(&modelPt, &fileFormat, &threeD, "FILEPATH", NULL, TRUE);

mdlSharedCell_createDefinitionElement(&sharedDefElem, cellName, FALSE);
mdlElmdscr_new( &cellHeaderPt, NULL, &sharedDefElem );

scanCritPt = mdlScanCriteria_create();
mdlScanCriteria_setModel (scanCritPt, modelPt);
mdlScanCriteria_setReturnType (scanCritPt, MSSCANCRIT_ITERATE_ELMDSCR ,FALSE,TRUE );

mdlScanCriteria_setElementCategory (scanCritPt,ELEMENT_CATEGORY_GRAPHICS);
mdlScanCriteria_setElmDscrCallback(scanCritPt, CreateCellDefCallb, (void *)cellHeaderPt);

mdlScanCriteria_scan (scanCritPt, NULL, NULL,NULL); // Returns END_OF_DGN


mdlSharedCell_addDefinitionElements( cellHeaderPt, &cellRot, &cellOrigo );

...

The callback:

static int CreateCellDefCallb(MSElementDescr *edP, void * targetDescrPt,	ScanCriteria *scP)
{
	MSElementDescrP copyDescrP;

	mdlElmdscr_duplicate (&copyDescrP, edP);
	mdlElmdscr_addToChain((MSElementDescrP)targetDescrPt, copyDescrP);
	return  SUCCESS;
}

Thanks in advance!