Reheating in Microwave Oven with Timer

On Shabbat, you may not put food in a microwave oven and have a timer turn it on, even if no light will be lit.  However, you may put the food into the microwave oven BEFORE sunset on Shabbat and have the timer turn on the microwave oven on Shabbat.
Note You must cover the microwave controls from before Shabbat.