[9.4] How do I preserve text formatting when changing the text of a field?

Empty fields revert to the default text attributes (12 pt Geneva plain). If you want to keep the current text attributes in a field you must leave some text in it, but it need only be a space. Instead of using:

set the text of cast blah = empty

use:

set the text of cast blah = " " -- there's a space in here