Get checkbox value in grid view instead of using foreach loop

I am using foreach loop to get value of checkbox from a grid view and update the records by geting the current user regID on checkbox CheckedChanged event.

In ASPX

   <Columns>
      <asp:TemplateField >
                            <ItemTemplate>
                                <asp:CheckBox ID="cbPaid" runat="server" AutoPostBack="true" OnCheckedChanged="cbPaid_CheckedChanged" Checked='<%# bool.Parse(Eval("status").ToString() == "Paid" ? "True": "False") %>' />
                            </ItemTemplate>
                        </asp:TemplateField>
                    </Columns>

And in aspx.cs

protected void cbPaid_CheckedChanged(object sender, EventArgs e)
{
    foreach (GridViewRow row in GdParticipants.Rows)
    {
        CheckBox cbPaid = (CheckBox)row.FindControl("cbPaid");

        if (cbPaid!=null && cbPaid.Checked == true)
        {
            string status = "Paid";
            int amount = Convert.ToInt32(ViewState["EventFee"]);
            DateTime date = DateTime.Now;
            string user = Session["user_id"].ToString();
            string regID = row.Cells[2].Text;

            string type = "Deposit";
            string account = "Participation";
            int balance = BAL.fetch_availableBalance();
            int total_balance = amount + balance;
            string detail = "Participant: "+regID+" fee has been Recieved";
            BAL.updateParticipants(regID, status, amount, user, date);
            BAL.saveBudgetTracking(type,account,amount,0,total_balance,detail,date);

        }
    }
    Response.Redirect("~/show_members.aspx");
}

The problem with this approach is whenever a new user updated a new record by checking a check box it will loop through the whole records and update the current change all over the previous records.

Anyone please guide me how can I get only the current regID from the row on which the checkbox was being checked and the checkbox value on checkbox-CheckedChanged event, instead of a loop?