Let me guess - you tracked a 3 or 4 part harmony and you want to split the voices between 3 or 4 French Horns, right? :)
The quickest way I found to do it is this. Say you have 4 French Horns or whatever...
Copy/paste from FH1 to FH2, 3 and 4. (I find it easier and quicker using shift-ctrl click&dragging the clip from FH1 to 2, 3, and 4.)
Select the 4 of them. Hit Alt-3 to open PRV so you have all 4 tracks in it.
In PRV...
Lock FR2, 3 and 4.
Delete unwanted voices from FH1. Lock FH1.
Unlock FH2. Delete unwanted voices in FH2. Lock FH2.
Unlock FH3.... etc...
I hope this help!
Sam