Hello.
I dont really know dota, but you only want to create a text above a tavern when someone writes "-cm"?
Have you checked the floating text actions? For example:
Floating Text - Create floating text that reads TEXT above TAVERN with Z offset 0.00, using font size 10.00, color (100.00%, 100.00%, 100.00%), and 0.00% transparency
or
Floating Text - Create floating text that reads TEXT at POINT with Z offset 0.00, using font size 10.00, color (100.00%, 100.00%, 100.00%), and 0.00% transparency