function calc_sum(form, SenderID) {

  var mycount, myprice;
  var myproduct = form.platforma.value; 

  switch (SenderID) {
    case 'chb':
      form.count.value = 1;
      myprice = ((form.fyz_osoba.checked) ? price(myproduct, 0) : price(myproduct, 1));
      mycount = 1;
    break;
    case 'num':
      form.fyz_osoba.checked = false;
      mycount = ((parseInt(form.count.value) > 0) ? (parseInt(form.count.value)) : NaN);
      myprice = price(myproduct, mycount);
    break;
  }

  form.price_per_1.value   = pados(myprice);
  form.price_total.value   = pados(myprice * mycount);
  form.price_total_d.value = pados(myprice * mycount * 1.20);

}

function pados(penez) {
  return Math.round(penez);
}

function check_all(formObj) {
  var i, field;
  var errormsg = '';
  for (var i=0;i < formObj.length;i++){
    fldObj = formObj.elements[i]; 
    switch(fldObj.name) {
      case 'jmeno':
        errormsg += (fldObj.value.length < 3) ? "Jméno nebo název společnosti\n" : "";
      break;
      case 'adresa':
        errormsg += (fldObj.value.length < 3) ? "PSČ, město\n" : "";
      break;
      case 'email':
        errormsg += (!fldObj.value.match('^[_a-zA-Z0-9\.\-]+@[_a-zA-Z0-9\.\-]+\.[a-zA-Z]{2,4}$')) ? "E-mail\n" : "";
      break;
    }
  }
  if (errormsg.length > 0) {
    result = confirm("Je možné, že některé položky nejsou správně vyplněné, zkontrolujte prosím položky:\n\n"+errormsg+"\nPokud chcete údaje opravit klikněte na tlačítko \"Storno\".\n");
    if (result) {      //if OK button hit  
      return true; 
    } else {            //if Cancel button hit 
      return false; 
    }
  }
  

}

function showonly(form, hid) {
  var i;
  var which;

  for (i = 1; i <= form.hcount.value; i++) {
    which = document.getElementById('h'+i);
    which.style.display="none";
  }
  which = document.getElementById(hid);
  which.style.display="inline";
}