Changed checkbox state when select is changed

I have a form and I'd like to make it so when the select box is changed, it's respective checkbox is checked automatically.

Could anyone shed any light on this? Let's say for the purpose the select boxes are 'select1, select2 etc..' and the checkboxes are 'checkbox1, checkbox2 etc..'

Screenshot of form

Snippet of table (first row)

<table width="820" class="content">
<thead>
<tr>
<th>Category</th>
<th>Code</th>
<th>Quantity</th>
<th>Issue?</th>
</tr>
</thead>
<tbody>
<tr>
<td>Beret</td>
<td><select name="select_beret">
<option value="8405-99-1278122">8405-99-1278122 : 48cm - 2 in stock</option><option value="8405-99-1278124">8405-99-1278124 : 50cm - 3 in stock</option><option value="8405-99-1278125">8405-99-1278125 : 51cm - 1 in stock</option></select>
</td>
<td><input type="text" name ="qty_beret"></td>
<td><input type="checkbox" name="checkbox_beret" value="Y">
</td>
</tr>
  </tbody>
  </table

Many thanks