You should be able to use an auto-enter calculation that reformats this for you without needing any script. If you use "self" (without the quotes) to refer to the contents of the field, you can then copy and paste this same expression into multiple field definitions should this be needed. By making this happen at the data level, your field will be automatically self correcting whereever you place it on your layouts.
Do do what you want with a script, you can pass the Table Occurrence (NOT the layout) name and field name as a script parameter. I recommend this expression, with your actual names inserted in place of "yourTable::YourField": GetFieldName ( YourTable::YourField ). This expression will automatically adjust should you use manage | Database to rename the field.
In your script, you can then use GetField( Get ( ScriptParameter ) ) to reference the contents of the field and you can use Set Field By Name [ Get ( ScriptParameter ) ;....] to modify the contents of the same field.
Thank you, Phil!
A little "SELF" knowledge was just the ticket.