[jQuery] Validate textbox (required=true) on combobox selected value

[ciupaz]

Hi all,
I have to validate a textbox if the user select a particular value in
a combobox.
For example, if the user select the "Specify new color" in the
following combobox:



<select id="color" name="color">
       <option value="-1">Specify new color</option>
       <option value="1">Red</option>
       <option value="2">Green</option>
       <option value="3">Blue</option>
       <option value="4">White</option>
       <option value="5">Black</option>
</select>

I have to validate the following textbox:

<input id="newColor" name="newColor" type="text" />


with the Validate Plugin:


rules: {
         newColor: {
             required: ??????
       },


How can I accomplish this?

Thanks in advance.

Luis.