Try this trick:
Set up a script to use Show Custom Dialog to display the field contents. Set the field in the portal row, or a button next to it to perform the script.
Thanks for the response.
That might be useful in some instances, but it won't help me right now because: 1) it doesn't display the font and color settings of the block of text and 2) the text can't be edited. I didn't think to mention those requirements.
Any other ideas?
This won't fix things completely the way you want, but if you place a button to the right of the field, you can view the dialog and still edit the field.
It's a bit clunky, but you might get what you need by experimenting with the New Window script command instead of Show Custom Dialog.
Using window commands to
open the new window
Hide/lock the status area
Go to layout showing the text in a text field.
Prevent user abort
Allow user abort
close the new window
Can give you a kind of modal dialog with formatted text in a field they can edit.