arcgis desktop - How to move an existing line to a parallel offset of another existing polyline

I'm currently trying to modify an existing line to be offset x distance from another existing polyline, is there any tool/addon that does that? I currently use Copy Parallel and create a dummy line that I move/snap my line to. I was just wondering if there was any way to directly specify that I want an existing line to be offset parallel from another line x units.