Trigger Target Disk Mode on MBP

Anyone out there know if there is a way to trigger target disk mode when something like lets say, a thunderbolt cable is plugged into one of the computers?

Here's the situation:

I have a macbook pro, but I need to do my work on a tower because I work in 3D animation, but I love having the portability of the macbook pro. My thinking is to maybe set up a system where the macbook pro will always have the boot disk, and when I need the power, I'll hook it up to the tower, but when I don't, or need to travel, unplug it and I'm off.

The problem with this though is that it can be tedious. The laptop needs to be shut down, then turned back on while holding down "T", then when its finally ready, hook it up, and start up the tower. If there was some way to speed up this step, by maybe some form of trigger that is detected and the laptop goes through the steps its self to get into disk mode, that would be great. I'm looking at possibly getting a Henge Dock to keep things organized.

Any ideas? Thanks.