Launch form with parameters: how can I get back information from the called form?

Epicor ERP 10
9

Using this code:
LaunchFormOptions LFO = new LaunchFormOptions();
LFO.ContextValue = new DataView(ds.Tables[“UD20”]);
LFO.IsModal = false;
LFO.SuppressFormSearch = true;
LFO.CallBackMethod = MyCallBackHandler(oTrans, CallBackArgs);
ProcessCaller.LaunchForm(oTrans, “UDSUBSEL”, LFO);

void MyCallBackHandler(object sender, object CallBackArgs)
{
    // verify there is CallBack args
    if (CallBackArgs == null) return;
    EpiMessageBox.Show("CallBack message:" + CallBackArgs.ToString());
}

I receive the error " Cannot implicitly convert type ‘void’ to ‘Ice.Lib.Framework.ProcessCallerCallBack’ "

What am I doing wrong here? (Besides trying to be a programmer)