Expression boxes or "calculated values" (as they are called in 2010) don't take bindings. You can set up an expression box based on a main data source - I'll assume that's what you mean by "binding". Using SharePoint's 2010 List Forms, you can't take a list and create multiple items in a repeating section from a single text entry. You'd have to know where to break it. I suppose you could build your own parser and look for linebreaks, but that's definitely not a valid solution to any problem these days. Please describe what you are trying to do at a high level. My guess is that you are trying to solve the wrong problem.