var kurz = 30.1260; 
  var maxCelychCisel = 10; 
  var maxDesatinnychCiselSkk = 3; 
  var maxDesatinnychCiselEur = 4; 

  function ibaCisla(text, max) { 
  var cnt = text.length; 
  var ret = ''; 
  var nemamBodku = true; 
  var predBodkou = 0; 
  var zaBodkou = 0; 
  for (i=0;i<cnt;i++) { 
  var znak = text.substring(i,i+1); 
  if (znak == ',') {znak = '.';} 
  if (znak >= '0' && znak <= '9') { 
  // max. celych cisel 
  if (nemamBodku) { 
  if (predBodkou<maxCelychCisel) { 
  ret = ret + znak; 
  predBodkou++; 
  } 
  // max. desatinnych sicel; 
  } else { 
  if (zaBodkou<max) { 
  ret = ret + znak; 
  zaBodkou++; 
  } 
  } 
  } 
  if (znak == '.' && nemamBodku) { 
  nemamBodku = false; 
  ret = ret + znak; 
  } 
  } 
  if (ret=='.') {ret = '';} 
  return ret; 
  } 
  
  function writeCurr(skk, eur, event) { 
  // filter specialnych klaves 
  if ((event.keyCode>34 && event.keyCode<41)) {return;} 
  if (skk == null) { 
  eur = ibaCisla(eur,maxDesatinnychCiselEur); 
  skk = (eur*kurz); 
  if (skk == 0) {skk = '';} 
  } else { 
  skk = ibaCisla(skk,maxDesatinnychCiselSkk); 
  eur = (skk/kurz).toFixed(maxDesatinnychCiselEur)*1; 
  if (eur == 0) {eur = '';} 
  } 
  if (document.getElementById('inputSkk').value!=skk) {document.getElementById('inputSkk').value = skk;} 
  if (document.getElementById('inputEur').value!=eur) {document.getElementById('inputEur').value = eur;} 
  }