var mn_format;
var mn_pocet_select;
var mn_pocet;

function init(){
  if(mn_format = document.getElementById("mn_format")) {
      mn_format.onchange = function(){fireMnFormatChanged();};
      mn_pocet_select = document.getElementById("mn_pocet_select");
      mn_pocet = document.getElementById("mn_pocet");
      fireMnFormatChanged();
  }
}

function fireMnFormatChanged() {
  var selectedIndex = mn_format.selectedIndex;
  if( mn_format[selectedIndex].value == 'vizitky' ) {
    mn_pocet_select.style.display = "";
    mn_pocet.style.display = "none";
    mn_pocet_select.disabled = false;
    mn_pocet.disabled = true;
  }else {
    mn_pocet_select.style.display = "none";
    mn_pocet.style.display = "";
    mn_pocet_select.disabled = true;
    mn_pocet.disabled = false;
  }
}