Hi following is my html table

<table id="grdtable">
<tr><td>Charge</td><td>start</td><td>End</td><td>No</td><td>Total</td></tr>
<tr><td>7</td><td>100</td><td>200</td><td>100</td><td>700</td></tr>
<tr><td>8</td><td>10</td><td>100</td><td>90</td><td>720</td></tr>
<tr><td>9</td><td>20</td><td>50</td><td>30</td><td>270</td></tr>
</table>

ts output is as follows

Charge     start     End     No     Total
7              100     200     100     700
8               10     100       90        720
9               20     50       30        270

my requiremt is on the click event of button i want add the the result in a variable using each function
var str="";
just like

str= 7 * 100=700
     8*90=720
     9*30=270
means multiplying first column with fourth column

how to do this

Regards

Baiju