Michael, you can put a thread on hold from an inbound reply, but in order to start the data flowing again you must stop and start the thread. DO NOT release the hold with the GUI or the message that caused the hold will not be sebt until the thread is cycled.
do the KILL on the reply instead of the KILLREPLY to keep any further messages from being sent, then exec the hcicmd in the background using & at the end of the line to put the thread on hold. the thread will stop sending because of the KILL and then go to hold state. will work on unix and windows.