function getScrollLayer() {
   if (document.layers) {
      return document.doelgroepContentLayer;
   } else if (document.getElementById) {
      return document.getElementById('doelgroepContentLayer');
   } else if (document.all) {
      return document.all.doelgroepContentLayer;
   }
}

function getPijltjesLayer() {
   if (document.layers) {
      return document.pijltjesLayer;
   } else if (document.getElementById) {
      return document.getElementById('pijltjesLayer');
   } else if (document.all) {
      return document.all.pijltjesLayer;
   }
}

function verScroll(dir, spd) {
   scrolltimer = null;
   var page = getScrollLayer();

   direction = dir;
   speed = parseInt(spd);
   var x_pos = parseInt(page.style.left);
   var layerWidth = parseInt(page.scrollWidth);

   if (direction == "le" && x_pos > (650-layerWidth)) {
      page.style.left = (x_pos - (speed));
   } else if (direction == "ri" && x_pos < 0) {
      page.style.left = (x_pos + (speed));                  
   }
   scrolltimer = setTimeout("verScroll(direction,speed)", 1);
}

function stopScroll() {
   clearTimeout(scrolltimer);
}

function scrollToSelected() {
   var page = getScrollLayer();
   var layerWidth = parseInt(page.scrollWidth);

   if (layerWidth > 680) {
      getPijltjesLayer().style.visibility = 'visible';
   }

   var selectedDG = null;
   if (document.getElementById) {
      selectedDG= document.getElementById('selDoelgroep');
   }
   else if (document.all) {
      selectedDG = document.all.selDoelgroep;
   }

   var x_pos_selDG = parseInt(selectedDG.offsetLeft);

   if (x_pos_selDG > 0 && x_pos_selDG < 700) {
      // do nothing de doelgroep is zichtbaar
   } else if (x_pos_selDG < 0) {
      // dit kan eigenlijk niet
   } else if (x_pos_selDG > 636) {
      // scroll naar links
      page.style.left = 636 - x_pos_selDG;
   }
}