joanaazevedo:
You will need to use the Global Variable
GLOB_SCALE to read the current scale, then, depending on your intensions, add some commands based on that value. I suggest looking at some Graphisoft Object symbols that have this feature to get some ideas about how it can work.
You should add a Signature to your Profile (click the Profile button near the top of this page) with your ArchiCAD version and operating system (see mine for an example) for more accurate help in this forum.
David