Alright, I have finished the adjustable target range for you. You can download it Here.
To install and use it, simply download the file, "Weapon%20Range.chernarus", go to your documents, and there will be an ArmA 2 folder. go into that, double click on the "mission" folder, and place the file in there. You will then be able to access it in the editor. If you have any problems or you just need my help to tweak it, feel free to ask. If needed, I could make an adjustable Pistol range. :D Hope you like it.