It is safe to call any mouse routine even when a mouse is not present.

Returns Carry Flag as set when a Mouse Event is waiting. Mouse Movement by itself does not usually trigger an event. Unless, the movement was an attempt to move the mouse outside of it's bounds. For example, beyond the top of the screen. Of course, Mouse button clicks and releases always generate events.

If %1 is provided, a jump to %1 will occur when an event is waiting.

See also: MouseRead, MousePreview and MouseOverflow.