select control group when using dunnet's method in c# and JMP

Question

I am trying to automate calculation of oneway analysis with dunnet's method but I am encountering below pop up after calling the last line of code. I need to automatically select the control group so calculation will proceed. If anyone has knowledge on incorporating JMP with c#, please i need your help. Thanks a lot.

    private void onewayButton_Click(object sender, System.EventArgs e)
    {
        JMP.Document doc;
        JMP.Oneway ow;

        startJMP();
        doc = myJMP.OpenDocument(jmpSampleDataDir + "analgesics.jmp");

        ow = doc.CreateOneway();
        ow.LaunchAddX("drug");
        ow.LaunchAddY("pain");
        ow.Launch();
        ow.CompareMeans(JMP.OnewayCompareConstants.occWithControl, true);
    }