Field security based visibility

Hello,

I planned to write a field-based security system for classic client from scratch . I managed to inject modification control for each and every field by a generic setup. But I also need visibility control. Is there any way to control shown or printed value of any field in any table beforehand generically? I mean, say that a user has no right to see value of a field, I will let him see the textbox but with an empty value (blank or zero). The starting point is to activate the change log management but what should be the next step?

Regards.