How to reduce the execution time for stored procedure using cursors in sql

SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO
    ALTER procedure [dbo].[SP_GETFIFOCOST](@pid nvarchar(250)) as
    Begin
    Declare @qty decimal(18,2),@cost decimal(18,2),@line int
    Declare @qty1 decimal(18,2),@cost1 decimal(18,2),@line1 int
    Declare @fqty decimal(18,2)
    set @fqty=0
    Declare MyCur Cursor for select QTY_IN,UNIT_COST,LINE from STOCKDETAILS  where STOCK_JR in ('IN','GR','TR','SA','OS','SR','AS','OG','PO') and PRODUCT_NO=@pid order by STOCK_DATE
    Open MyCur
    Declare MyCur1 Cursor for select QTY_OUT,UNIT_COST,LINE from STOCKDETAILS  where STOCK_JR in ('OU','IS','SJ','TR','SA','CS','AS','PR','DO') and PRODUCT_NO=@pid order by STOCK_DATE
    Open MyCur1
    if @fqty=0
    begin
    Fetch Next From MyCur1 into @qty1,@cost1,@line1
    Fetch Next From MyCur into @qty,@cost,@line
    End
    While @@Fetch_Status=0
    Begin
    if @qty>@qty1
    begin
    set @qty=@qty-@qty1
    update STOCKDETAILS set FIFO_COST=@cost where LINE=@line1
    set @fqty=@fqty+@qty
    if @fqty>0
    begin
    Fetch Next From MyCur1 into @qty1,@cost1,@line1
    set @fqty=@qty-@qty1
    update STOCKDETAILS set FIFO_COST=@cost where LINE=@line1
    end
    end
    if @qty<@qty1
    begin
    set @fqty=@qty-@qty1
    update STOCKDETAILS set FIFO_COST=@cost where LINE=@line1
    if @fqty<0
    begin
    Fetch Next From MyCur into @qty,@cost,@line
    Fetch Next From MyCur1 into @qty1,@cost1,@line1
    set @qty1=@fqty-@qty1
    set @fqty=@qty+@qty1
    if @fqty>0
    begin
    set @qty=@qty+@qty1
    end
    update STOCKDETAILS set FIFO_COST=@cost where LINE=@line1
    end
    end
    if @fqty=0
    begin
    update STOCKDETAILS set FIFO_COST=@cost where LINE=@line1
    Fetch Next From MyCur1 into @qty1,@cost1,@line1
    Fetch Next From MyCur into @qty,@cost,@line
    End
    End
    Close MyCur1
    Close MyCur
    Deallocate MyCur1
    Deallocate MyCur
    End

try
               {
                   str = "select distinct PRODUCT_NO from PRODUCT order by PRODUCT_NO";
                   cn.Open();
                   cmd.CommandText = str;
                   cmd.Connection = cn;
                   dr = cmd.ExecuteReader();
                   try
                   {
                       while (dr.Read())
                       {
                           using (DbCommand cmdb = cn.CreateCommand())
                           {
                               try
                               {
                                   cmdb.Connection = cn;
                                   cmdb.CommandText = "SP_GETFIFOCOST";
                                   cmdb.CommandType = CommandType.StoredProcedure;
                                   var parameter = cmdb.CreateParameter();
                                   parameter.ParameterName = "@pid";
                                   parameter.Value = dr.GetValue(0).ToString();
                                   cmdb.Parameters.Add(parameter);
                                   cmdb.ExecuteNonQuery();
                               }
                               catch (Exception Ex) { }
                           }
                           //progressBar1.Value++;
                       }
                       dr.Close();
                       cn.Close();
                   }
                   catch (Exception Ex)
                   {
                       dr.Close();
                       cn.Close();
                   }