Brake in-line lever
 

Can we install an "in-line" brake lever for our rear disc brake? Right now we activate the disc with a bar-end lever. We want to be able to use the bar-end lever to shave off speed and use the in line lever to be able to modulate braking and give the rim brake a brake, so to speak. Thanks in advance.

Yes. In-line brake levers are just that. However, I'd recommend running the brake cable from your bar-end 'drag brake' control under the handlebar tape to help with the alignment of the cable's entry to the in-line brake control.

If you haven't seen it, Park Tools has a nice guide on how these are installed with Campy ergo brifters. Your bar-end installation would be similar: http://www.parktool.com/repair/readhowto.asp?id=146