Simon,

I have never tried to use the IR543 to send the programming sequence. I will try it tonight to see if it is possible and what exactly is happening when you do so. I can see all the X-10 activity and will track the Pronto / IR543 transmissions. I would suggest using a Maxi Controller or Touchlinc to do the programming.
You don’t have to press anything on the switch before you send it information; the sequence is what puts the switch into the programming mode. Let me play around and I will give you some better suggestions later. If you would like and don’t want to buy a Maxi controller, I could send you a one to use and you could return it when you are finished programming the switch. Let me know.

Chris