Add Comma Delimited String To A Hiddenfield On Page?

I have a gridview that displays client data. The first column on each row for the gridview is a checkbox. The second column on the gridview is client name and the third column is account holder. The user can select checkboxes (on multiple rows) to modify data (account holder).

I want to add clientName column value in a comma delimited string to a hiddenfield on my page. How do I do that using javascript, as I do not want to use postback and looping through each row on the grid to get the checkbox status. When a checkbox is checked, it should append the hiddenfield value.

I am getting the hiddenfield value as blank no matter what checkboxes are checked. I also know that my code is not targeting the correct row to get ClientName (row where checkbox is checked).

function RowClick(CheckBox)
{
var BaseControl = document.getElementById('<%= this.myGrid.ClientID %>');
var TargetControl = document.getElementById('MyHiddenField');

[Code]....