Edit Specific Text In NSTextView

[jpeezy]

Say I have the string "this is a test, this is a test" in a textView. I only want the user to be able to edit the word "test" (both instances) and I need the textView to shrink and grow with what the user enters. I have a method that uses a regex to get the ranges (I'd imagine this isn't optimal, maybe NSScanner would be better?). Anyway, 2 problems I'm having. 1) The ranges need to be adjusted based on what the user enters. 2) ONLY the "test" ranges are editable.

I'm just looking for a bit of guidance in which classes to use. Will I need to use LayoutManager/TextContainers?

Thanks