datepicker on passed textbox clientid in javascript

I have a gridview and template field (textbox) control. on GridView_RowDataBound I want to find the control and pass the control id to a javascript which will set datepicker on that textbox here is how I am doing but its not working...can u please help.
Code behind
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protected void GridView1_RowDataBound(object sender, GridViewRowEventArgs e)
{
// string strParams;
/// string id;

if (e.Row.RowType == DataControlRowType.DataRow)
{
//Get Instanse of all the objects
DropDownList dd1 = (DropDownList)e.Row.FindControl("DDBillingMonths");
TextBox tb1 = (TextBox)e.Row.FindControl("txtCurrBillUnits");
TextBox tb2 = (TextBox)e.Row.FindControl("txtAmountBDueDate");
TextBox tb3 = (TextBox)e.Row.FindControl(& ...