sum totalamount in crystal report

if {actualguesting.paymentmode}='CASH' then
sum({actualguesting.totalamount})

If ComboBox1.Text = "Shift 1" Then
    Dim dt As Date = DateTimePicker1.Text
    Dim rpt As New endofshift() 'The report you created.
    Dim MyCommand As New SqlCommand()
    Dim myDS2 As New loghistory() 'The DataSet you created.
    Dim myDA2 As New SqlDataAdapter()
    Dim myDS As New DSactualguesting() 'The DataSet you created.
    Dim myDA As New SqlDataAdapter()
    Dim cn As New SqlConnection(ConnectString())

    Try

        MyCommand.Connection = cn
        MyCommand.CommandText = "Select * from actualguesting where shift = 1 and datecheckin='" + dt + "'"
        MyCommand.CommandType = CommandType.Text
        myDA.SelectCommand = MyCommand
        myDA.Fill(myDS, "actualguesting")

        myDA.SelectCommand.CommandText = "Select * from loghistory where username='" + Login.txtuser.Text + "'"
        myDA.Fill(myDS, "loghistory")

        myDS.EnforceConstraints = False
        rpt.SetDataSource(myDS)
        CrystalReportViewer1.ReportSource = rpt
    Catch Excep As Exception
        MessageBox.Show(Excep.Message, "Error", MessageBoxButtons.OK, MessageBoxIcon.Error)
    End Try
endif

6:00 AM - 2:00 PM = shift 1
2:00 PM - 10:00 PM = shift 2
10:00 PM -6:00 AM = shift 3