Alternative way to enter construction line mode

 From:  immortalx
7395.1 
Hi guys. Coming from sketchup, I'm so used to the measure tool that I'm trying to replicate some of its functionality with construction lines.
When drawing Clines, I use the numerical input to specify accurate distances, but it feels awkward having to do that with my left hand while i keep the mouse button pressed with my right hand.
Is there a way to enter construction-line-mode (from within any tool) without clicking and dragging, or is it hardcoded? For example, left click and hold (at the first point) for more than 1 sec--->enters Cline mode. One can then release the mouse button, type in a distance (with the right hand :) ) and click once more to set the direction.
Alternatively, a left click with a modifier button could also be a nice option.