Notes, at least as far back as version 4, has provided access to the formula language in any text field. If you place a valid @-formula into a text field and press SHIFT+F9, the formula will be computed and the value for the text field replaced with the results of the formula.

You may be wondering why you would ever want to do this. Well, here's one example. Let's say you're filling out a project document. The project document asks for a due date. You would like the due date to be 45 days from now. You could guess at what 45 days from now would be, or you could get your calendar out and count, or you could use this new trick. Go into an empty text field and type in:
@Adjust(@Today; 0; 0; 45; 0; 0; 0)
And press SHIFT+F9. The actual date 45 days from now will be the value of the field, which you can use in your project document.

Just about any valid formula can be used in this technique. Obviously, the formula must be hard-coded (instead of using variables), but it's a very handy technique to put into your toolbox.