Req: Disable Birthdate Field if already filled in

[hurrican]

I'd like to disable the birthday field (let it be seen, but no changes can be made) with the following criteria.....

IF Birthdate is NULL (ie: user didn't put anything in @ Registration or editing profile) Allow user to choose a birthdate/year

OR

IF Birthdate is NOT NULL, but year IS NULL, allow YEAR to be input (while keeping month/day in the database, and appending the year)

OR

If Birthdate DAY, MONTH, and YEAR are all filled in, DISABLE Allowing editing of the BIRTHDAY field.

I've kind of gotten it halfway to work, the only thing I've got a problem with right now is this....

MEMBER.PHP

PHP Code:

     // Set birthday fields right here!
     if ($bbuserinfo[birthday] == '0000-00-00') {
        $daydefaultselected = "selected";
        $monthdefaultselected = "selected";
### ADDED 4/1/06 ###
     eval("\$birthday = \"".gettemplate("register_birthday")."\";");
### END ADDED 4/1/06 ###
     } else {
        $birthday = explode("-",$bbuserinfo[birthday]);
        $dayname = "day".$birthday[2]."selected";
        $$dayname = "selected";
        $monthname = "month".$birthday[1]."selected";
        $$monthname = "selected";
        if (date("Y")>$birthday[0] && $birthday[0]!='0000')
           $year = $birthday[0];
### ADDED 4/1/06 ###
     eval("\$birthday = \"".gettemplate("register_birthday_no_edit")."\";");
### END ADDED 4/1/06 ###
     } 


I created a new Template with the "Register Birthday" template, and added "disable" at the end of the table names, making the birthday fields not be editable. However, once un-editable, if you submit your profile again, it erases the birthdate in the database, and then the user can choose another birthday.. Anyone who can help would be greatly appreciated!