My next issue requires some deep thinking, I suspect. My screen is situated in front of a window. If the window is open, lowering the screen will result in damage (the screen is worth some 3'000$). I have an EnOcean reed contact on the window, which transmits a wireless signal. The signal is picked up by a transceiver and gets into a linux server. At the moment, this is used for triggering a burglar alarm if the windows opens while the alarm is armed.

Now the question is: what might be the best way to have the RTi controller test the status of the reed contact? The pseudocode would be;
if (reed == open) {abort init macro};
In principle, I can program the linux server to do whatever is needed for the RTi to check - but which is the most functional way to do so? Any advice will be highly appreciated.

All you need to do is send a open string and closed string to the Rti. Make an event in the Rti to when it receives this string to set an xp flag. Now make your open and close shade macros first test this flag and not run if the window is open. You could even make this trigger a popup to say hey the windows open so the shades won't close.

Thanks - very kind and helpful. This makes a lot of sense and I will implement it as you say.