tell application "iTunes"
set apDevices to (get every AirPlay device whose available is true)
if apDevices is {} then display dialog "No Airplay devices available." buttons {"Cancel"}
set apNames to (get name of every AirPlay device whose available is true)
set selAirplayDevices to (get name of every AirPlay device whose selected is true)
set chosenNames to choose from list apNames default items selAirplayDevices with prompt "Select Airplay device:" with multiple selections allowed
if chosenNames is false then return
set apChoices to {}
repeat with i from 1 to length of apNames
if item i of apNames is in chosenNames then set end of apChoices to item i of apDevices
end repeat
set current AirPlay devices to apChoices
end tell