This project is one I've had on the books for a very long time. I designed my motor mount specifically to hold the laser module 3" away from the center of the router. The most daunting part of this project was creating the custom screen set for Mach 3. In the end, google was my best friend... or as I often refer to it as "Mother Google".
I found and utilized a free application called MachScreen to modify/customize the standard 1024 screen set that comes default with Mach 3. The other thing that mother google provided was help figuring out how to write a script to tell Mach 3 what I wanted it to do upon pressing the button.
Here's that bit of code for any that are interested:
Xmove = -3 'adjust this for X move distance
Ymove = 0 'adjust this for Y move distance
Code "G91 G0 X" &Xmove & "Y" &Ymove ' makes an incremental move the distances that you set
While IsMoving () ' waits while that happens
Code "G90" 'goes back to absolute moves
DoOEMButton (1008) 'zeros the X and Y DROs