Protecting fields in Access?

Is there any way I could protect alteration by user of such fields as foreign keys and primary keys that are generated by the software (autonumber)?

Also, is there any way of validating a field so that first letter will be converted to capital or has to be inputted as capital but otherwise the field is only limited by its size, i.e.di I really have to specify 40 "C" characters after the "capital only" rule?