checkbox validation with additional text box

[seanwpb]

i have the following

<tr>
     
     <td class="style14" align="left">Current Medical Problems: 
       <input type="checkbox" name="medicalproblemsnone" value="None"><span class="style16">None</span>
       <input type="checkbox" name="medicalproblemsdiabetes" value="Diabetes"><span class="style16">Diabetes</span>
       <input type="checkbox" name="medicalproblemsHypertension" value="Hypertension"><span class="style16">Hypertension</span>
       <input type="checkbox" name="medicalproblemsCholesterol" value="Cholesterol"><span class="style16">Cholesterol</span>
       <input type="checkbox" name="medicalproblemsThyroid" value="Thyroid"><span class="style16">Thyroid</span><br>
     <span class="style16">&nbsp;&nbsp;Other&nbsp;&nbsp;</span><input name="medicalproblemsother" class='fourtywide' type="text" maxlength="50"/>
     </td>
           
     
   </tr>

i need to validate to make sure at least one of the check boxes is checked, but if they check the None box the others shouldnt be checked and if they click the None the text box should be empty as well. i have searched all over and cant find a solution. i currently have a validation function successfully checking all my other radio buttons, and text boxes but this one is beyond my knowledge. any help would be great