The function inside draggable window is not appearing

Hi, this is my problem: Before I make the draggable window, "GUI.Window" on OnGUI is running, but after I make the draggable window and cut the code inside OnGUI into the function that parameter on "GUI.Window" requires a function (in this case: DraggableWindowFunction), the function inside GUI.Window is not running, while before that, the code is perfectly running.

Here is the code:

void OnGUI()
    {
        // If GUIHolder opened variable is true
        if (GUIHolder.opened) // When tab button on keyboard was pressed, the variable opened is true
        {
            // Set the User draggableWindow to active window
            User.draggableWindow = GUI.Window(0, User.draggableWindow, DraggableWindowFunction, GUIContent.none);
        }
    }

void DraggableWindowFunction(int windowID)
    {
        Event e = Event.current; // For locating the current mouse position

        // If GUIHolder opened variable is true
        if (GUIHolder.opened)
        {
            // Draw the texture
            GUI.DrawTexture(User.backgroundRect, User.imageBackground);

            // Call the DrawBoxes method
            DrawBoxes(); // Drawing some boxes into screen

            // Set the window to be draggable window
            GUI.DragWindow(new Rect(0, 0, 450, 20));
        }

While the code inside DraggableWindowFunction is on OnGUI, the code inside still running, but after I move out the code from OnGUI to DraggableWindowFunction, the code is not running, only the GUI.Window itself on the OnGUI function, and the GUI.DragWindow on DraggableWindowFunction.

Your answer much appreciated!

Thank you

Yes it would not update !!! Its in a window not an OnGUI Nor Function Update() so put the functions in function Update or Late Update or OnGUI there is no other way, unless you call the functions using function update, & a bool!