C++/CLI Correct use of threads and problems with Appendtext

Question

I will try to be brief. For a school project I need a UI with a command prompt (textbox) and a log window (richtextbox).

When we type a command,System::Void MyForm::cmd_textBox_KeyDown(System::Object^ sender, KeyEventArgs^ e) called another function (in another .cpp) to process it and the function is displayed in my richtextbox.

Some functions send usb frames and receive responses via the interrupt function : System::Void MyForm::serialPort1_DataReceived(System::Object^ sender, System::IO::Ports::SerialDataReceivedEventArgs^ e)

My concern is the following:

• should my command be launched in another thread than the one managed by the UI?
• when we receive a USB frame and I want to do an AppendText in my richtextbox, the Appentext is sometimes done with a lot of delays (sometimes after other commands).

Currently I update my log via this function, but it still has a delay. If I replace BeginInvoke with Invoke the UI freezes.

void MyForm::Update_log_TextBox(String^ text, Color text_color)
{
    Update_log_TextBox_Delegate^ action = gcnew Update_log_TextBox_Delegate(this, &MyForm::Worker);
    this->BeginInvoke(action, text, text_color);
}

void MyForm::Worker(String^ text, Color text_color)
{
    MyForm::log_TextBox->SelectionColor = text_color;
    MyForm::log_TextBox->AppendText(text);
}

Do you have any solutions for me please?

Sorry for my broken English it is not my native language