Linkage attributes

Hello

I have a problem. I'm trying to add attribute to element but I haven't 
still done it. So I decided to write a program to testing but it doesn't 
work too. What I do wrong ? Why function mdlLinkage_appendToElement 
cannot add attribute to element ?

test.mc:

#include <mdl.h>
#include <mselems.h>
#include <stdio.h>
#include <string.h>

#include "test.h"

#include <mselemen.fdf>
#include <mscurrtr.fdf>
#include <mssystem.fdf>
#include <mslinkge.fdf>
#include <msdialog.fdf>

#define TESTID             999

#define ID_GRAF			1

int main(int argc, char *argv[])
{
     DPoint3d p[2] = {{0.0,0.0,0.0},
					 {50.0,50.0,0.0}};
     MSElement el;
	LinkageHeader header;
	Attr att;
	AttrRecv copy;
	UInt fPos;
	char napis[200];
	

	memset(&header, 0, sizeof(LinkageHeader));
	header.info	=0;
     header.remote	=0;
     header.modified	=0;
	header.user = 1;
	header.primaryID = TESTID;
	att.id = 500;
	
     mdlCurrTrans_begin ();
     mdlCurrTrans_masterUnitsIdentity(TRUE);

     if (mdlLine_create(&el, NULL, p) != SUCCESS)
     {
         printf("nie uda³o siê utworzyæ elementu!\n");
         return 1;
     }
     mdlCurrTrans_end ();

	mdlElement_display(&el, NORMALDRAW);
	

	if(mdlLinkage_appendToElement(&el, &header, &att, ID_GRAF, NULL) != 
SUCCESS)
	{
		mdlDialog_openInfoBox("Nie podpiêto atrubutu");
		mdlSystem_unloadMdlProgram("userlink");
		return  1;
	}
	else
		mdlDialog_openInfoBox("Podpieto atrybut");
	
	//mdlElement_rewrite(&el, NULL, fPos);
	fPos = mdlElement_add(&el);
	if (fPos<= 0L)
     {
         printf("nie uda³o siê dodaæ elementu do pliku!\n");
		mdlSystem_unloadMdlProgram("userlink");
         return 1;
     }
	
	if (mdlLinkage_extractFromElement( &copy, &el, TESTID, ID_GRAF,NULL, 
NULL, NULL) != SUCCESS)
	{
		mdlDialog_openInfoBox("Nie zczytano atrybutu");
		mdlSystem_unloadMdlProgram("userlink");
		return  1;
	}
	else
	{	
		sprintf(napis, "Atrybut ma warto¶æ = %d", copy.id);
		mdlDialog_openInfoBox(napis);
	}
	mdlSystem_unloadMdlProgram("userlink");
     return  0;	/*meaningless int value returned by main */
}


test.h:

#include <mselems.h>

typedef struct attr {
	int id;
} Attr;

typedef struct attr_Recv {
	LinkageHeader header;
	int id;
} AttrRecv;

test.mt

#include "test.h"

createDataDef (attr, TEST);



I hope you can help me.
Thanks
Krzysztof