Hi program,
I think one solution would be to use Js / jQuery to analyse what's in your field.
You can insert Js / jQuery into your field by clicking on the blue arrow at the bottom of the modal box where you set your field.
The field's name (where you've to put Js) is "Script (JS)".
If you've other questions or if it doesn't work don't hesitate to come back to us.
Good continuation.
Ness