I don't think it would be possible without creating problems. First of all the cable would have hard bends running from the tops of the lever to the in-line lever's base. Also the loop would be so close in places as to cost you the use of that part of the bar, or create traps where your hand might get snagged when you change hand positions.

If you want dual position braking, buy a cheap or used pair of brake levers with along the bar cable routing and do it right.