function Kalender(form, df)
{
  var tt;
	var mx = 768 / 2 - 170;
	var my = screen.width / 2 - 220;	
  tt = "fileadmin/kalender/kalender.php?form=" + form + "&feld=" + df;
  KalenderWin = window.open(tt,"Kalender","left=" + my + ",top=" + mx + ",resizable=yes,dependent=yes,toolbar=no,menubar=no,scrollbars=no,height=340,width=440");
}

function checkthree(a,b,c,but)
{
	var a1 = document.getElementById(a).value;

  var a2 = document.getElementById(b).value;
  
  var a3 = document.getElementById(c).value;
  
  if ( (a1!="0") && (a2!="") && (a3!="") )
  {
    document.getElementById(but).disabled = false;
  }
  else
  {
    document.getElementById(but).disabled = true;
  }
}