How can I keep track of a section of text in a Dynamic TextField in AS3

Question

I want to be able to apply non-style attributes to sections of text in a TextField. For example characters 30-45 will be set to animate in a certain direction.

As this field is editable characters 30-45 may no longer be at 30-45 if the text is edited in any way.

Can anyone think of an elegant way to keep track of which characters had the attributes applied to them?