Auto sunroof with a 555 timer?

This is my first posting on this site. I am a student learning electronics, but my knowledge of op amps and logic gates is very limited. I am trying to wire up a auto close circuit for the sunroof in my car. My sunroof module does not seem to use any over current sense stopping circuitry. It keeps track of its position by use of wheel that is spun as it opens or closes. It looks like some sort of infrared sense between the spokes of the wheel.

It has a 12V supply and then two 12V signals on either side of a switch to open or close the sunroof. When I supply power and ground to the module all I have to do is apply 12 volts to one signal wire or the other and the module does the rest. It does have a nice feature that allows a one quick press to automatically retract the sunroof but does not have this for the forward position.

Looking around on the internet I found this 555 monostable timer circuit.
http://www.bowdenshobbycircuits.info/page9.htm
There is only 30mA of current on both signal wires so it was well within what the 555 could handle. I hooked up the close side of the switch inline with pin 2 on the 555 and set the output(pin 3) to the module.

It worked great. 100uF was just enough to get the sunroof completely closed from the rearmost position. Once it is going however, there is no way to stop it. That seems just a little too unsafe to me. Is there anything simple I could add to it to kill the operation. Perhaps a 12V signal from the open switch while it is closing to stop it completely. I just need a way to interrupt it and I can't find a good direction to go in. Thanks in advance!