private class refDICARD
        {
            public string ref_DICARD { get; set; }
            public string ref_DIHOUR { get; set; }
        }

        private List<refDICARD> listDicard = new List<refDICARD>();
        ....

            //載入時數表
            string SQL = "SELECT DICARD,DIHOUR FROM RXV_DICARD";
            DataTable dt = RxConnection.RxConn.GetDataTable(SQL, "DICARD");

            if (dt.Rows.Count > 0)
            {
                for (int i = 0; i < dt.Rows.Count; i++)
                {
                    listDicard.Add(new refDICARD { ref_DICARD = dt.Rows[i]["DICARD"].ToString(), ref_DIHOUR = dt.Rows[i]["DIHOUR"].ToString() });
                }
            }

         //計算時數

            decimal SumTT = 0;

            for (int i = 0; i < rxSpread1.ActiveSheet.Rows.Count; i++)
            {
                string dicard = this.rxSpread1.ActiveSheet.Cells.Get(i, 1).Text;
                if (dicard.Trim() != "")
                {
                    refDICARD dd = listDicard.Find(delegate(refDICARD d) { return d.ref_DICARD == dicard; });
                    SumTT += decimal.Parse(dd.ref_DIHOUR);
                }
            }
            this.txtHour.Text = SumTT.ToString();