i want to calculate the values on gridview itself on keyup

i have a gridview 10 columns.

1s is a serial no

2nd is checkbox

3-8 is database value

9th is a textbox

and 10th is a total

i want a javascript code in which user will enter value in the textbox column and should calculate(addition) with the 8th column database value and show the total in 10th column

 

1	2	3	4	5	6	7	8	9	10
serial no	database value	database value	database value	database value	database value	database value	database value	textbox	total

 

on keyup  event  want a javascript code which will take 8th column and 9th textbox value and sum it in 10th column