How can I enable the Checkbox on CheckedChanged event to update only the select row in the GridView?

Code file:
Partial Class CallDetail Inherits System.Web.UI.Page Protected Sub CheckBox1_CheckedChanged(ByVal sender As Object, ByVal e As System.EventArgs) For Each row As GridViewRow In GridView1.Rows If row.RowType = DataControlRowType.DataRow Then Dim CheckBox1 As CheckBox = DirectCast(row.FindControl("CheckBox1"), CheckBox) If CheckBox1.Checked Then TextBox3.Text = "checked" Else TextBox3.Text = "" End If End If Next End Sub End Class Html File:
<asp:GridView ID="GridView1" runat="server" AutoGenerateColumns="False" DataSourceID="CallDetailUpdate" DataKeyNames="AutoNo"> <Columns> ...