Sigh.
If you're talking about direction (inward or outward), you must be assigning a velocity to the field propagation, because if it were infinite, there'd be no direction. The whole field would just appear or disappear.
Now let's suppose you turn on your magnet and leave it on for a year. However fast you imagine it to be, the field will reach to some region of space. Since you left it on for a year, it will take a year to collapse at the same speed. But you must admit that the the field close to the apparatus will collape almost immediately after you flick the switch. So in order for the "inward collapse" to reach the apparatus just as you are flicking on the switch, the collapse has to begin much earlier--a year earlier, in fact.