Maybe you could use the MouseX(MyCanvas)and MouseY(MyCanvas) commands?
or maybe use the $205 to detect when your user enters the canvas and then use MouseXSpeed(MyCanvas)or $203 to see if the mouse is moving and then if it's not, do your popup.
or maybe use the $205 to detect when your user enters the canvas and then use MouseXSpeed(MyCanvas)or $203 to see if the mouse is moving and then if it's not, do your popup.