How to make a sum of number fields to single field in contact form 7 in wordpress

below is the code of table in contact form 7,

<table>
<tr>
<th>RX #</th>
<th>Amount</th>
</tr>
<tr>
<td>[number RX1 placeholder "RX1"]</td>
<td>[number RX1Amount placeholder "RX1 Amount"]</td>
</tr>
<tr>
<td>[number RX2 placeholder "RX2"]</td>
<td>[number RX2Amount placeholder "RX2 Amount"]</td>
</tr>
<tr>
<td>[number RX3 placeholder "RX3"]</td>
<td>[number RX3Amount placeholder "RX3 Amount"]</td>
</tr>
<tr>
<td>[number RX4 placeholder "RX4"]</td>
<td>[number RX4Amount placeholder "RX4 Amount"]</td>
</tr>
<tr>
<td>[number RX5 placeholder "RX5"]</td>
<td>[number RX5Amount placeholder "RX5 Amount"]</td>
</tr>
<tr>
<td>Total Amount</td>
<td>[number TotalAmount]</td>
</tr>
</table>

i want sum the amount column in such a way that when i enter number/amount in any of the field it should be updated in last total row, if i enter number/amount in more than one row, sum of all rows should be updated in last total row.

can any one help me out?

via Chebli Mohamed