It is certainly able to do what you want.
It is possible to disassemble the shifter and reassemble it with the circular ring (part 2 in
this diagram) with the square hole in it in the wrong orientation and thus limit the shifters movement.
Correctly assembled it should be able to rotate about 150 degrees.
My barcons provide ample travel for triple chainrings. I've even seen one used on a tandem with four chainrings.