set the hide (drill- down OK ) at run time

In my drill down crystal report (vs.net 2005) , I want to set the hide (drill- down OK ) option for the group header at run time based on the user preference.
How can do that programmatically?
Thx

VB Code:

Private Sub configureCrystalreports()
        MyCrystalReportViewer.Visible = False
        OVBReport = New OVBRpt
        Dim myds As New DataSet
        myds = mcsData.OVB1(CreateQuery())
        If myds.Tables(0).Rows.Count > 0 Then
            lblNorecords.Visible = False
            OVBReport.SetDataSource(myds)
            MyCrystalReportViewer.ReportSource = OVBReport
            MyCrystalReportViewer.Width = ToolStrip1.Width() - 180
            MyCrystalReportViewer.Visible = True
        Else
            MyCrystalReportViewer.Visible = False
            lblNorecords.Visible = True
        End If
    End Sub