Help with MessageBoxes

greetings to all,

i created a form (EletronicDiary) which has a button to open another form(Add New Appointment) -->

Code:

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Appointment_AddScreen^ addApointForm = gcnew Appointment_AddScreen();
                        addApointForm->ShowDialog();

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when i click on CANCEL, a messageBox appears to cofirm my decision(with buttons YES NO). My problem is no matter my decision of Yes or No, the add new appointment form closes. Please i need advice on what to do so that when i click on NO, my form doesnt close. Below is the code

Code:

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private: System::Void btnAddCancel_Click(System::Object^  sender, System::EventArgs^  e) {
                        System::Windows::Forms::DialogResult result;
                        result = MessageBox::Show("Are you sure you want to exit?\nUnsaved entries will be lost!","Confirm Exit",MessageBoxButtons::YesNo,MessageBoxIcon::Warning);

                        if (result == System::Windows::Forms::DialogResult::Yes)
                                {
                                        this->Close();
                                }
                }

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attached is an image for futher clarification

NB even if the IF statement is not present, the form still closes after Yes or No is clicked