Get max of a running sum in a column grouped by week

DECLARE @tmp TABLE(ID INT IDENTITY(1,1), aDATE DATETIME, Pallets INT)

INSERT INTO @tmp (aDATE, Pallets)
VALUES('2014-09-29', 4),('2014-09-30', 5),('2014-10-01', 6),('2014-10-02', 1),('2014-10-06', -2),('2014-10-07', 1),('2014-10-08', -3)

SELECT t2.ID, t2.aDATE, DATEPART(wk, t2.aDATE) AS aWeek, SUM(t1.Pallets) AS RunningSum
FROM @tmp AS t1 INNER JOIN (
    SELECT ID, aDATE, DATEPART(wk, aDATE) AS aWeek, Pallets
    FROM @tmp
    ) AS t2 ON t1.ID <= t2.ID
GROUP BY t2.ID, t2.aDATE, DATEPART(wk, t2.aDATE)
ORDER BY t2.ID

ID   aDATE                     aWeek   RunningSum
1   2014-09-29 00:00:00.000    40     4
2   2014-09-30 00:00:00.000    40     9
3   2014-10-01 00:00:00.000    40     15
4   2014-10-02 00:00:00.000    40     16
5   2014-10-06 00:00:00.000    41     14
6   2014-10-07 00:00:00.000    41     15
7   2014-10-08 00:00:00.000    41     12

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;
using System.Data.SqlClient;
using ICSDB;
using Microsoft.Reporting.WinForms;



namespace ICS.EnterpriseResourcePlaning
{
    public partial class WarehouseMovementsReportForm : Form
    {

        private DataTable DtWarehouseMovements = new DataTable();
        int _WarehouseID = 0;
        double _RuningSum = 0;

        public WarehouseMovementsReportForm(int warehouseID=0)
        {
            _WarehouseID = warehouseID;
            InitializeComponent();
            AddColumnsToDataTable(DtWarehouseMovements);
        }

        private DataTable AddColumnsToDataTable(DataTable dt)
        {
            dt.Columns.Add("Datum", typeof(DateTime));
            dt.Columns.Add("Bewegung", typeof(string));
            dt.Columns.Add("Artikel", typeof(string));
            dt.Columns.Add("ANummer", typeof(string));
            dt.Columns.Add("LSNummer", typeof(string));
            dt.Columns.Add("Paletten", typeof(double));
            dt.Columns.Add("Faktor", typeof(double));
            dt.Columns.Add("Handling", typeof(double));
            dt.Columns.Add("Week", typeof(int));
            dt.Columns.Add("RuningSum", typeof(double));
            dt.Columns.Add("Lagergeld", typeof(double));
            return dt;
        }


        public void FillDataTable()
        {
            //Clear Rows in DataTable that Fills the Report
            DtWarehouseMovements.Rows.Clear();
            _RuningSum = 0;

            DateTime minDate = DateTime.Today;
            DateTime maxDate = DateTime.Today;
            minDate = dtpMinDate.Value;
            maxDate = dtpMaxDate.Value;

            WarehouseMovements tblWarehouseMovements = new WarehouseMovements();
            WarehouseMovementTypes tblWarehouseMovementTypes = new WarehouseMovementTypes();
            WarehouseItems tblWarehouseItems = new WarehouseItems();

            tblWarehouseMovements.Orderer = "Date,ID";

            tblWarehouseMovements.Parameters.Clear();
            tblWarehouseMovements.SetParameter("Deleted", false);
            tblWarehouseMovements.AddParameter("Date", minDate.AddDays(-1), "", SQLTable.Operator.Conditional.UND, SQLTable.Operator.Rational.größer);
            tblWarehouseMovements.AddParameter("Date", maxDate.AddDays(1), "", SQLTable.Operator.Conditional.UND, SQLTable.Operator.Rational.kleiner);
            tblWarehouseMovements.SetParameter("WarehouseID", _WarehouseID);

            DataTable dtWM = tblWarehouseMovements.DataTable;

            _RuningSum = SumToDate(minDate);

            foreach (DataRow row in dtWM.Rows)
            {              
                DataRow Nrow = DtWarehouseMovements.NewRow();

                double Lagergeld = 0;

                //Datum
                DateTime date = DateTime.MinValue;
                DateTime.TryParse(row["Date"].ToString(), out date);

                //Bewegung
                int movementID = 0;
                int.TryParse(row["WarehouseMovementTypeID"].ToString(), out movementID);
                string bewegung = tblWarehouseMovementTypes.MovementName(movementID);

                //Artikel data
                int itemID = 0;
                int.TryParse(row["WarehouseItemID"].ToString(), out itemID);
                string artikel = string.Empty;
                string aNummer = string.Empty;
                double pFaktor = 0;
                tblWarehouseItems.WarehouseItemData(itemID, out artikel, out aNummer, out pFaktor);

                //Paletten
                double palleten = 0;
                double.TryParse(row["Pallets"].ToString(), out palleten);

                int movementTypeFactor = tblWarehouseMovementTypes.MovementFactor(movementID);

                _RuningSum += palleten * movementTypeFactor;

                if (_RuningSum > Lagergeld)
                    Lagergeld = _RuningSum;
         
                //Week
                int week = 0;
                week = DateAdapter.Week.WeekNumber(date);


                Nrow["Datum"] = date;
                Nrow["Bewegung"] = bewegung;
                Nrow["Artikel"] = artikel;
                Nrow["ANummer"] = aNummer;
                Nrow["LSNummer"] = row["LSNumber"].ToString();
                Nrow["Paletten"] = palleten;
                Nrow["Faktor"] = pFaktor;
                Nrow["Week"] = week;
                Nrow["RuningSum"] = _RuningSum;
                Nrow["Lagergeld"] = Lagergeld;
                DtWarehouseMovements.Rows.Add(Nrow);
            }

        }

        private double SumToDate(DateTime date)
        {
            double sum = 0;

            string command = " SELECT SUM(dbo.WarehouseMovementTypes.Factor * dbo.WarehouseMovements.Pallets) AS Summe " +
                                " FROM     dbo.WarehouseMovements INNER JOIN " +
                                " dbo.WarehouseMovementTypes ON dbo.WarehouseMovements.WarehouseMovementTypeID = dbo.WarehouseMovementTypes.ID " +
                                " WHERE  (dbo.WarehouseMovements.WarehouseID = @WarehouseID) AND (dbo.WarehouseMovements.Date < @Date) AND (dbo.WarehouseMovements.Deleted = 0)";

            SqlConnection conn = ICSConnections.ICSDB;
            SqlCommand cmd = new SqlCommand(command, conn);
            cmd.Parameters.Add("@Date", SqlDbType.NVarChar).Value = date;
            cmd.Parameters.Add("@WarehouseID", SqlDbType.Int).Value = _WarehouseID;

            double.TryParse(cmd.ExecuteScalar().ToString(), out sum);

            return sum;
        }

        private void button1_Click(object sender, EventArgs e)
        {
            RefreshReport();
        }

        private void RefreshReport()
        {

            FillDataTable();

            rptWarehouseMovements.ProcessingMode = ProcessingMode.Local;
            ReportDataSource source = new ReportDataSource("WarehouseMovementsDS", DtWarehouseMovements);
            rptWarehouseMovements.LocalReport.DataSources.Clear();
            rptWarehouseMovements.LocalReport.DataSources.Add(source);

            this.rptWarehouseMovements.RefreshReport();
        }

    }
}