If you mean a "current selection" box then you can in the script use HidePrefix to hide field values from the current selection box. You can still show that field in a listbox but the values will not appear in the "Current Selection Box.
It would look something like this in your script. SET HidePrefix = '_';
Any field renamed with an underscore prefix for example _Language will be hidden.
Again not quite sure if this is what you are looking for.