While getting a cell value in row am getting error Object reference not set to Instance of Object ?

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C#

Gridview

DevExpress

Am trying to get focused row cell value and previous row cell value of focused row. I used this code

object eachprice = gridView1.GetRowCellValue(gridView1.FocusedRowHandle,gridView1.Columns["Price"])

this code get the value of price in focused row

object eachprice = gridView1.GetRowCellValue(gridView1.FocusedRowHandle-1, gridView1.Columns["Price"]);

but this code didn't get the cell value of previous row. it show null value so i get error "Object reference not set to instance of Object"

this is my code

private void discountcol()
    {

        if ((getdisc == tempstr) && (rownumber >= 1))
        {
            int focusedcount = gridView1.FocusedRowHandle;

            t1.Text = "";
            t1.Text = getdisc;

            object eachprice = gridView1.GetRowCellValue(focusedcount-1, gridView1.Columns["Price"]);
            t2.Text = eachprice.ToString();

            if (!(t2.Text == string.Empty))
            {
                decimal pricedecimal = Convert.ToDecimal(t2.Text);
                object eachdiscount = gridView1.GetRowCellValue(gridView1.FocusedRowHandle, gridView1.Columns["Price"]);
                decimal eachdisdecimal = Convert.ToDecimal(eachdiscount);
                decimal tempdiscountprice = -(pricedecimal * (eachdisdecimal / 100));  // -ve calculation
                t3.Text = tempdiscountprice.ToString("N2");

                gridView1.SetRowCellValue(gridView1.FocusedRowHandle, gridView1.Columns["Price"], t3.Text);

                if (getdisc == tempstr)
                {
                    PricQuan.UnboundType = DevExpress.Data.UnboundColumnType.Decimal;
                    PricQuan.UnboundExpression = " 1 * [Price]";

                    TaxinAmount.UnboundType = DevExpress.Data.UnboundColumnType.Decimal;
                    TaxinAmount.UnboundExpression = " ([Price] * ([TaxInPercentage] / 100.0)) * 1 ";
                }
                else
                {
                    //PricQuan.UnboundType = DevExpress.Data.UnboundColumnType.Decimal;
                    //PricQuan.UnboundExpression = " Round([Quantity] * [Price], 2)";

                    //TaxinAmount.UnboundType = DevExpress.Data.UnboundColumnType.Decimal;
                    //TaxinAmount.UnboundExpression = " ([Price] * ([TaxInPercentage] / 100.0)) * [Quantity] ";
                }

            }

        }
        else
        {

        }
    }