Sounds like you are dealing with a DSL (Domain Specific Language). What you are looking for sounds exactly like XText. Here’s an extract from the page:
Xtext is a framework/tool for development of external textual DSLs. Just describe your very own DSL using Xtext’s simple EBNF grammar language and the generator will create a parser, an AST-meta model (implemented in EMF) as well as a full-featured Eclipse Text Editor from that.
Also, check out this video which is an interview with one of the people behind it. I’m sure you’ll take it from here 🙂
You may also want to check out this plugin. Not exactly what you are looking for, but could be a nice start.