How to detect user input as "zero" and force user to give valid reason in text box given

html code is given as below : <tr> <td>i</td> <td colspan="3">Temperature Of Warming Bin/Chute(140F -150F/60C - 65C)</td> <td>1</td> <td> class="col-sm-12"> <input required type="number" class="form-control" name="b_1_1" id="b_1_1" min="0" max="1"> </div> </td> </tr> And my comment box in html is : <div class="form-group"> <textarea class="form-control" placeholder="Comments" name="Comments" id="Comments" rows="6"></textarea></div> How to force a user to give valid reason if the user input is "0" instead "1" in a textarea below before proceeding to next form. I have a total of 5 forms.