Dynamic Text problem

Ok here is my problem.
I’ve made some text with a scrollbar. That text is Dynamic Text. I want to make some of the text in one size and some of the text in a smaler size. But if I e.g. mark a sentence that I want to have in a smaler size, all the text in the text-box-thing gets small. If I do the same thing with Static Text it works perfectly. Is it posible to make some of the text in a Dynamic Text box small and the other way around?

(I hope you understand:p Its not so easy to explain)