Create Calendar Entry via c#

I was successfully able to open new Appointment thru C# code, but for some reason Who field is not editable. I would like to just open the new Calendar Entry thru C# program with given dates, and let the user fill in Subject, Attendees, Location etc…

LNDocument.ReplaceItemValue(“Form”, “Appointment”);

                        //Type of the appointment, means:

                        LNDocument.ReplaceItemValue("AppointmentType", "Meeting");



                        LNDocument.ReplaceItemValue("Subject", "");



                        // Set Confidential Level (Public=1 or Private=0) 

                        LNDocument.ReplaceItemValue("$PublicAccess", "1");

                        LNDocument.ReplaceItemValue("$ExpandGroups", "3");

                        //Add Start&End Time of your event

                        LNDocument.ReplaceItemValue("CALENDARDATETIME", StartDate);

                        LNDocument.ReplaceItemValue("StartDateTime", StartDate);

                        LNDocument.ReplaceItemValue("EndDateTime", EndDate);

                        LNDocument.ReplaceItemValue("StartDate", StartDate);

                        //Infos in The Body

                        LNDocument.ReplaceItemValue("Body", "");

                        LNDocument.ComputeWithForm(true, false);

                        LNDocument.Save(false, false, false);





                        System.Diagnostics.Process.Start(LNDocument.NotesURL);

Subject: Working when added

//Attendees LNDocument.ReplaceItemValue(“REQUIREDATTENDEES”, " ");

                            LNDocument.ReplaceItemValue("AltRequiredNames", " ");

                            LNDocument.ReplaceItemValue("OptionalAttendees", " ");

                                              



                            //Owner

                           LNDocument.ReplaceItemValue("Principal", " ");

                            LNDocument.ReplaceItemValue("Chair", " ");





                            //Location

                            LNDocument.ReplaceItemValue("Location", " ");

                            LNDocument.ReplaceItemValue("Room", " ");