Remove options from second dropdown box value based on selecting first drop down box value

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SQL-Server

HTML

PHP

I have two Drop down boxes with the same values on both... when i choose a value in 1st drop down , the second drop down must hide the chosen value and display remaining in the second drop down...am fetching drop down values from a table using php ...is this possible via design or using a query???

//1st drop down

<td><i><b>Rec_Series</b></i></td>
			<td><select id="rec" name="rec">
			 <?php     Show_Recseries($_POST['Region'],$brname[0]) ; ?>
			 </select>
			 </td>
			<script language="javascript">$('#rec').val("<?php echo $_POST['rec'];?>")</script>	

//2nd drop down

<td><i><b>Bill_Mac_id</b></i></td>
           <td><select id="brmacid" name="brmacid">
               <?php
                       Show_Mac_id($_POST['Region'],$brname[0]);
               ?>
       </select>
           </td>
           <script language="javascript">$('#brmacid').val("<?php echo $_POST['brmacid'];?>")</script>

can someone help me out?? Create a new fiddle - JSFiddle[^]

Thanks in advance

What I have tried:

I had tried to hide other drop down and got really confused..Do I need to change in function or in my php code???