HG can't do this by default, but it can be done easily. You need to write a script to check for the incoming X10 action (e.g., A1 ON) and then perform an action (e.g., B1 ON). You have different methods that you could use to incorporate this, but if it's as simple as my example then a wizard script is probably best. Simply specify the trigger event and the action when that event occurs. Make sure the script is enabled and you are good to go. If you want to do more complex actions requiring logic (e.g., if A1 ON and night turn B1 ON), then you will probably want to use one of the programming languages (C#, JS, etc).