I currently have a UM506 Universal Module opening and closing my garage door via a credit card remote....
Since most, if not all, garage doors are set up where the button signal toggles from the last direction, reverses, or stops based on the current state of the door, you really need a hardware indicator of the position of the door. The most reliable would be one that detects when the door is fully open.
I use a setup that
only allows X10 to close the door as I don't feel like compromising the security that my garage remote gives me. I've posted more on my setup elsewhere.
Also Dave_X10_L has a setup that works well for him that lets him know via BVC that when his door is open.
I have worked out a macro that would close the door from any position with a setup like yours but it relies on 3 timed signals reliably being sent from AHP. The failure of any of the 3 signals from the macro to reach the Universal Module could result in the door being left open. (You could blindfold me and put a soundproof headset over my head and I could push my garage button 3 times and guaranty that the door would be closed regardless of the starting position the door.)
If you search the forum, you can find more about both of our setups.
Also you can drop by in the evenings to
http://bdshost.com/ac/. Dave shows up most evenings.