Make a field mandatory for all users

Is there a way (in Enterprise Explorer version 10) to make a field mandatory on a screen for all users.

I want to make a combo-box mandatory in Customer Orders for all users.

I know it can be made mandatory by RMB- Properties-Mandatory and  then selecting the object from the list but that only does it for the user who is currently logged in. It doesn’t carry across to all profiles. I want to make the field mandatory for every profile. But I don’t want to alter the Base profile or personal profile.

Is there a back-end table I can modify it in?