__UI_ForceRedraw

__UI_ForceRedraw is a global variable that triggers a redraw for all form controls when it's set to True. When it's not set to True, controls are redrawn only when changes in their properties or state are detected.

__UI_ForceRedraw = True

It's automatically set back to False after the next form repaint is executed.

If you want to trigger a redraw for only a specific control, use the Redraw property:

Control(myControl).Redraw = True