Validation on a drop down menu

Validation on a drop down menu

Hello. I am attempting to create a validation rule for my form. if someone selects the other field, I would like to make the other licence box mandatory. I am using (below) for the validation

  1.  <script type="text/javascript" src="http://jzaefferer.github.com/jquery-validation/jquery.validate.js"></script>
The html I have is as follows.

  2. <input type="text" name="caa"  class="required" placeholder="Personal CAA/Licence Number"/>
  3.                 <select name="licence" class="required">
  4.                     <option value="">Type of licence held</option>
  5.                     <option value="JAR PPL(A)">JAR PPL(A)</option>
  6.                     <option value="JAR PPL(H)">JAR PPL(H)</option>
  7.                     <option value="JAR PPL(M)">JAR PPL(M)</option>
  8.                     <option value="NPPL">NPPL</option>
  9.                     <option value="JAR CPL(A)">JAR CPL(A)</option>
  10.                     <option value="JAR CPL(H)">JAR CPL(H)</option>
  11.                     <option value="ATPL(F)">ATPL(F)</option>
  12.                     <option value="ATPL(A)">ATPL(A)</option>
  13.                     <option value="ATPL(H)">ATPL(H)</option>
  14.                     <option value="Aircraft Engineer">Aircraft Engineer</option>
  15.                     <option value="None">None</option>
  16.                     <option value="Other">Other</option>
  17.                 </select><br />
  18.                 <input type="text" name="otherlicence" placeholder="Other licence type" /> <br />
Any help would be greatly appreciated.