update on button click along with validation

[srishree]

Hi,i had been working on a gridview which has textbox and button controls in the itemtemplate fields and few bound fields.my question is that i need to validate the number entered manually in the textbox is a valid entry or not on the button click attribute of the gridview row.if valid i need to update the data entered in the textbox with the existing value in the database......i wrote a javascript to validate tht the entry is valid,but this checks only for the first row of gridview and fails for all other rows........here is my javascript..... function fn_check(which) { var element_length = which.length; alert(which.gv1$ctl02$TextBox5.name); for (i=0;i