void mySliderCallback(enum mtouch_slider_names slidername)
{
    printf("The slider %d just changed its postion.\r\n", slidername);
}

main()
{
    ...

    MTOUCH_Slider_SetPositionChangedCallback(mySliderCallback);

    ...

    while(1)
    {
       MTOUCH_Service_Mainloop();
    }
}