Radio Button and Input Text relationship

I have a question… I have a radio button and below that an input text field. The first, if the user selects ‘Select Producer’, it generates a pop-up window with a list of all different Producers. The input text allows the user to type 1 or more (seperated by a comma) a specific Producer #.

However, the business owner believes that the users will get confussed and click on the radio button to Select Producer but type in the text the producer Number. I am at a loss what kind of JavaScript will prevent the user from typing in the Input Text if he clicked on Select Producer. Can anyone help?

<tr>
<br><td>
<font style=”Helvetica” color=”#CC6633″><div align=”right”><b>Producer</b></div></td>
<td>
<div align=”left”>
<input type=”radio” name=”Producer” value=”AllProd” tabindex=”5″ align=”left” checked><b>All</b></div></td>
</tr>
<tr>
<td>
</td>
<td>
<div align=”left”><input type=”radio” name=”Producer” value=”notAllProd” tabindex=”5″ align=”left” ><b>Select Producer</b></div></td>
</tr>
<tr>
<td>
</td>
<td>
<input type=”text” size=”15″ name=”PRODnum” maxlength=”13″ tabindex=”40″ class=”textNumber”>
</td>
</tr>
</tbody>
</table>
</td>

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