Backspace ability on a wrong Fixture Number

Hi HES,
 Can I ask for the ability to change what happens when I type in a wrong number on the command line for a fixture, so that when I see this error I can use the back space to delete one digit only instead of losing the whole group of digits that are on the command line.

Eg: I type 1233 (Error) I go and hit back space to get rid of that second 3 because is the fixture I wanted is 123, but the command line clears completely clears when I currently hit back space. Maybe programmers like this, but I don't, so maybe it needs to be an option. Thanks for looking at this.