Cannot apply indexing with [] to an expression of type 'obje

Question

protected void Deductions1_RowDataBound(object sender, System.Web.UI.WebControls.GridViewRowEventArgs e)
    {
        if (e.Row.RowType == DataControlRowType.DataRow)
        {
            CheckBox cb = (CheckBox)e.Row.FindControl("CheckBox2");
            if (cb.Checked == true)
                cb.Checked = false;
            int amnt = Convert.ToInt32(e.Row.DataItem["ded_amt"].ToString());
            tded.Text = Convert.ToString(tded.Text) + amnt;
        }
    }

at the place of e.iam getting a error like" Cannot apply indexing with [] to an expression of type 'object'"

please help what shell i do now....
please help me friends

thank you..