you guys can help me with this?
How much are you paying, and when is our homework dues?
Detecting when motion IS being sensed, when it BECOMES sensed, and when it BECOMES not sensed, are three different things. Which one(s) are of interest to you? What have you been able to to so far, to discover that motion is sensed?
Noticing when motion BECOMES sensed is illustrated in the state change detection example.
Noticing what time that happens, and doing something (or stopping doing something) some fixed time later is illustrated in the blink without delay example.