[Hrimthurs]

Hi there,
I am currently trying to find out how to alter parts of an image url through the selection of a dropdown.
I have something where the first dropdown changes the entire url:

<script language="javascript">
<!--
function ShowPic(sImage)
{
   document.ShowRoom.src = sImage;
}
// -->
</script> 
<form name="proof">
  <select name="design"  onChange="ShowPic(this.value)">
    <option value="1">Option 1</option>
    <option value="2">Option 2</option>
  </select>
  <select name="style">
    <option value="a">Option a</option>
    <option value="b">Option b</option>
  </select>
  <select name="finish">
    <option value="z">Option z</option>
    <option value="y">Option y</option>
  </select>
</form>
<img name="ShowRoom" src="images/outsidefront.jpg">

But I need to change parts of the url depending on the 3 chosen options on the 3 dropdowns.

<img src="http://www.domain.com/images/+variable++variable2++variable3+.jpg" />

Does anyone know a way to do this.