An IR motion sensor connected to your outside lights might work for you.
I have my sensors, which are built into the lamps, set to come on at 1/2 brightness at dusk and go off after 6 hrs, they can go dusk to dawn. Whatever the setting, if someone trips the sensor the lamp will come on full brightness for a set time, 5mins or so, if it is dark outside.
The lamps I have, cheapie Ocean State lamps, have a connection so you can link lights together. One on, all on. You can also buy these motion sensors as seperate units so you then wire it to your existing outside lights.
I have a floodlight on the rear of my garage. In this unit I disabled the light coming on at dusk bit so it only lights up when it is dark and 'something' trips it.