Delete measures in just one instrument

I'm about halfway through entering a piece from written down music, and about halfway through I've noticed that one of my instruments has three extra measures (I've accidentally duplicated them). I've tried deleting them, but that action (CTRL-Del) removes those measures for all the instruments, not just the one I messed up.

I have tried highlighting the remainder for that instrument, which is correct, to copy and paste back three measures earlier, but it seems that when I have to move the music to go from the first note to the last the first note is no longer selected, and SHIFT-select doesn't work.

Does anyone know of a quick work-around for either of these issues?

--
Helge