using harmony one on two of the same devices

-50 panasonic plasma
-onkyo 805
-ps3
-wii
-xbox 360
-hd-a20
- directv hr 21-100
-directv hr21-200
-sony 5 disc dvd player
-directv hr10-250(tivo)

How can i make my harmony one work on both the hr21-200 and hr21-100 with out working eachother at the same time , I thought of using an ir exstender but will that seperate the 2 dvrs if it goes through a ir exstender instead of using one ir and one rf, and ideads how to simplefy this

Thats tough, because since they receive the same signal as long as they both can catch the signal they will both change. If the RF can get it to a place where it will not catch the IR signal you will be fine. At one point I had one box in a closes with RF and an identical box under the TV and I never had any issues cause the IR signal could not get to the second box.