Checking for markers

I need a script that checks for markers of a specific name... that doesn't crash if they don't exist in the map.



What function can I use for this?|||New question: How do I spawn a group of units? Like, in the map editor only units in the "INITIAL" group spawn by default. If I want to make the spawn of certain enemy structures at the start of the game dependent on a variable (say, difficulty level) how would I do this? What's the function to spawn a group?