Sourcecode:

<script type="text/javascript">
function nDollar() 
{
var nKurs, nEuro, nDoll, nKurs2, nEuro2, nDoll2, Kurs2, Euro2, Doll2;

nKurs=0;
nEuro=0;
nDoll=0;
nKurs2=0;
nEuro2=0;
nDoll2=0;

if (document.nForm.nKurs.value!="") {
   Kurs2=String(document.nForm.nKurs.value);
   Kurs2=Kurs2.replace(",",".");
   nKurs=parseFloat(Kurs2);
}
if (document.nForm.nEuro.value!="") {
   Euro2=String(document.nForm.nEuro.value);
   Euro2=Euro2.replace(",",".");
   nEuro=parseFloat(Euro2);
}
if (document.nForm.nDoll.value!="") {
   Doll2=String(document.nForm.nDoll.value);
   Doll2=Doll2.replace(",",".");
   nDoll=parseFloat(Doll2);
}
if (document.nForm.nKurs2.value!="") {
   Kurs2=String(document.nForm.nKurs2.value);
   Kurs2=Kurs2.replace(",",".");
   nKurs2=parseFloat(Kurs2);
}
if (document.nForm.nEuro2.value!="") {
   Euro2=String(document.nForm.nEuro2.value);
   Euro2=Euro2.replace(",",".");
   nEuro2=parseFloat(Euro2);
}
if (document.nForm.nDoll2.value!="") {
   Doll2=String(document.nForm.nDoll2.value);
   Doll2=Doll2.replace(",",".");
   nDoll2=parseFloat(Doll2);
}

if (nKurs>0) {
   nDoll=nEuro/nKurs*100;
}

document.nForm.nKurs.value=nKurs.toFixed(4);
document.nForm.nEuro.value=nEuro.toFixed(2);
document.nForm.nDoll.value=nDoll.toFixed(2);

if (nKurs2>0) {
   nEuro2=nDoll2/nKurs2*100;
}

document.nForm.nKurs2.value=nKurs2.toFixed(3);
document.nForm.nEuro2.value=nEuro2.toFixed(2);
document.nForm.nDoll2.value=nDoll2.toFixed(2);

 }
-->
</script>

 <form name="nForm">
 <table align="center" cellspacing="2" border="0">

   <tr>
    <th>Kurs</th>
    <th>Euro</th>
    <th>Dollar</th>

    <th width="40"></th>

    <th>Kurs</th>
    <th>Dollar</th>
    <th>Euro</th>
   </tr>

   <tr height="20">
    <th width="70">
      <input class="txtNumb" name="nKurs" type="text" size="9" maxlength="10" value="64.4883">
    </th>
    <th width="70">
      <input class="txtNumb" name="nEuro" type="text" size="9" maxlength="10" value="100.00">
    </th>
    <th>
      <input class="txtNumb" name="nDoll" type="text" size="9" maxlength="10" value="">
    </th>

    <th width="40"></th>

    <th width="70">
      <input class="txtNumb" name="nKurs2" type="text" size="9" maxlength="10" value="155.055">
    </th>
    <th width="70">
      <input class="txtNumb" name="nDoll2" type="text" size="9" maxlength="10" value="100.00">
    </th>
    <th>
      <input class="txtNumb" name="nEuro2" type="text" size="9" maxlength="10" value="">
    </th>

   </tr>

   <tr height="30">
    <th colspan="3">
      <p>Kurs und Euro veränderbar
    </th>
    <th width="40"></th>
    <th colspan="3">
      <p>Kurs und Dollar veränderbar
    </th>
   </tr>

   <tr height="50">
    <th colspan="7">
      <input type="button" value="     Berechnen     " onClick="nDollar()">
    </th>
   </tr>
  </table>

  </form>