I'm currently trying to incorporate quarter tones into a piece for my contemporary composition class. There are a few specific moments where i'd like to change the note on one staff to a quarter flat or a quarter sharp. My teacher showed us that you could create a custom expression that gave us both the symbols needed and could shift the pitch to the correct sound for playback. 

My problem is I only want to change the pitch for one note on one staff. Instead, the expression seems to affect everything (All 3 staves). I see there's a way to change where the expression is assigned (to current staff, to all staffs, etc) but that doesn't seem to do anything. There must be another issue at hand. 

It might be worth mentioning that I also can't change the instrument sound on one part without all the other parts changing to that instrument. They all seem to be linked in someway. I already deleted all linked parts under: Documents > Manage Parts, and nothings changed.