dropdown list changing content of textarea

how do i get index.php&color=blur to appear if a user selects blue

[mrowton]

I'm have a cms that lets users syndicate content using javascript. They can change the type of content they get based on what they put in the source URL. Something like this:

<script language="javascript" src="index.php?color=blue&shape=round"></script>

I'd like to help them construct this URL using javascript in a form. I keep thinking of Google Adsense as a good example. (The part where you can select the size and color of the ad)

Lets say the user has the option of specifying shape and color.

<form>
<select name="color">
 <option value="">Select a Color</option>
 <option value="color=blue">blue</option>
 <option value="color=red">red</option>
</select>
<select name="shape">
 <option value="">Select a Shape</option>
 <option value="&shape=round">round</option>
 <option value="&shape=square">square</option>
</select>
<textarea name="output">
<script language="javascript" src="index.php?**ADD FIELDS HERE**"></script> 
</textarea>
</form>

It looks like I just need to add the select values onto the end of index.php? inside the text area.

As a further example, if they want content that is "round" and "blue" then I would need to provide the below in the text area.

<script language="javascript" src="index.php?color=blue&shape=round"></script>

I know very little about javascript but can't seem to even grasp this enough to search for examples.

Can anyone help me out here?

[phillipandrews]

<form>

<select name="color">
<option value="">Select a Color</option>
<option value="blue">blue</option>
<option value="red">red</option>
</select>

<select name="shape">
<option value="">Select a Shape</option>
<option value="round">round</option>
<option value="square">square</option>
</select>

<input type="submit">
</form>
That would be the best way to go, since you don't know javascript. then do all of your coding on the server side