session variable and aspx problem

Question

my Customer_TotalSales.aspx page have 4 control such as.....DropdownList1,DropdownList2,Datepicker1,Datepicker2 and 1 button

button_click event code  of Customer_TotalSales.aspx are below...

protected void Button1_Click1(object sender, EventArgs e)

    {        

 Session["@FromCustomerName"] = DropDownList1.SelectedValue;

      Session["@ToCustomerName"] = DropDownList2.SelectedValue;

      Session["@FromDate"] = DatePicker1.SelectedDate;

      Session["@ToDate"] = DatePicker2.SelectedDate;

      Response.Redirect("SessionVariable.aspx");

}

Another aspx SessionVariable.aspx  its have 4 lable control which hold the session variable value and pass these value to crystal report Viewer control...

public partial class SessionVariable : System.Web.UI.Page

{     

    protected void Page_Load(object sender, EventArgs e)

    {

        LabFromCustomer.Text = Session["@FromCustomerName"].ToString();

        LabToCustomer.Text = Session["@ToCustomerName"].ToString();

        LabFromDate.Text = Session["@FromDate"].ToString();

        LabToDate.Text = Session["@ToDate"].ToString();

        CrystalReportViewer1.Visible = false;

        CrystalReportViewer1.Visible = true;

        CrystalReportSource1.Report.FileName = Server.MapPath("Reports/Customer_totalsalesTest.rpt");

        ParameterDiscreteValue objDiscreteValue;

        ParameterField objParameterField;

        //Set value for first parameter.....

        objDiscreteValue = new ParameterDiscreteValue();

        objDiscreteValue.Value = LabFromDate.Text;

        objParameterField = CrystalReportViewer1.ParameterFieldInfo["@FromDate"];

        objParameterField.CurrentValues.Add(objDiscreteValue);

        CrystalReportViewer1.ParameterFieldInfo.Add(objParameterField);

        objParameterField = CrystalReportViewer1.ParameterFieldInfo["@ToDate"];

        //Set value for second parameter......

        objDiscreteValue = new ParameterDiscreteValue();

        objDiscreteValue.Value = LabToDate.Text;

        objParameterField.CurrentValues.Add(objDiscreteValue);

        CrystalReportViewer1.ParameterFieldInfo.Add(objParameterField);

        //Set value for Third parameter......

        objDiscreteValue = new ParameterDiscreteValue();

        objDiscreteValue.Value = LabFromCustomer.Text;

        objParameterField = CrystalReportViewer1.ParameterFieldInfo["@FromCustomerName"];

        objParameterField.CurrentValues.Add(objDiscreteValue);

        CrystalReportViewer1.ParameterFieldInfo.Add(objParameterField);

        objDiscreteValue = new ParameterDiscreteValue();

        objParameterField = CrystalReportViewer1.ParameterFieldInfo["@ToCustomerName"];

        objDiscreteValue.Value = LabToCustomer.Text;

        objParameterField.CurrentValues.Add(objDiscreteValue);

        CrystalReportViewer1.ParameterFieldInfo.Add(objParameterField);

        CrystalReportViewer1.ReportSourceID = "CrystalReportSource1";

    }

}

when i Execute First page then asking for 4 value DropdownList1,DropdownList2,Datepicker1,Datepicker2 ..i choose these value when i click button then SessionVariable.aspx execute and show the crystal report everything working nice till now ...

when i want change the value of parameter then i need to close the page and Re-Execute the page ........

 please  help me ...how can i Changed the parameter value to change theese value   DropdownList1,DropdownList2,Datepicker1,Datepicker2 in one time execution.....whats i edit in my code for that.......