tekstveld bepaalt keuzeveld mee

<script type="text/javascript"> 
function verander(arr) { 
   var el = document.getElementById('sel'); 
   el.options.length = 0; 
      for(var i = 0; i< arr.length; i++ ) { 
        el.options[el.options.length] = new Option(arr[i], arr[i]); 
         el.options[el.options.length] = new Option("Other"); 
  
      } 
} 
</script> 

<table width="600" border="0" align="center"> 
  <tr> 
    <td width="20%" height="30" valign="top">woonplaats:</td> 
    <td height="30" colspan="2" valign="top"><input name="titel" type="text" id="titel" size="20" onkeyup="verander([this.value]);" /></td> 
  </tr> 
  <tr> 
    <td width="20%" height="30" valign="top">woonplaats 1</td> 
    <td height="30" valign="top"> 
    
    <label> 
      <select id="sel"> 
        <option value="bezig">Eerst een woonplaats invullen</option> 
      </select> 
    </label> 
    
    </td> 
    <td height="30" valign="top"><input readonly name="other" type="text" id="other" size="20" /></td> 
  </tr> 
  
  <tr> 
    <td height="30" valign="top">woonplaats 2</td> 
    <td height="30" valign="top"> 
     <label> 
      <select id="sel"> 
        <option value="bezig">Eerst een woonplaats invullen</option> 
      </select> 
    </label> 
    </td> 
    <td height="30" valign="top"><input readonly name="other2" type="text" id="other2" size="20" /></td> 
  </tr> 
  
  <tr> 
    <td width="20%" height="30" valign="top">&nbsp;</td> 
    <td height="30" colspan="2" valign="top"><input name="submit" type="submit" value="Invoegen" /></td> 
  </tr> 
</table> 

<script type="text/javascript"> 
function verander(arr) { 
   var el = document.getElementById('sel'); 
   el.options.length = 0; 
      for(var i = 0; i< arr.length; i++ ) { 
        el.options[el.options.length] = new Option(arr[i], arr[i]); 
         el.options[el.options.length] = new Option("Other"); 
 
      } 
} 
</script> 
 
<table width="600" border="0" align="center"> 
  <tr> 
    <td width="20%" height="30" valign="top">woonplaats:</td> 
    <td height="30" colspan="2" valign="top"><input name="titel" type="text" id="titel" size="20" onkeyup="verander([this.value]);" /></td> 
  </tr> 
  <tr> 
    <td width="20%" height="30" valign="top">woonplaats 1</td> 
    <td height="30" valign="top"> 
 
    <label> 
      <select id="sel"> 
        <option value="bezig">Eerst een woonplaats invullen</option> 
      </select> 
    </label> 
 
    </td> 
    <td height="30" valign="top"><input readonly name="other" type="text" id="other" size="20" /></td> 
  </tr> 
 
  <tr> 
    <td height="30" valign="top">woonplaats 2</td> 
    <td height="30" valign="top"> 
     <label> 
      <select id="sel"> 
        <option value="bezig">Eerst een woonplaats invullen</option> 
      </select> 
    </label> 
    </td> 
    <td height="30" valign="top"><input readonly name="other2" type="text" id="other2" size="20" /></td> 
  </tr> 
 
  <tr> 
    <td width="20%" height="30" valign="top">&nbsp;</td> 
    <td height="30" colspan="2" valign="top"><input name="submit" type="submit" value="Invoegen" /></td> 
  </tr> 
</table>