Adding User Value to field in back end

I am interested to know if there is a way to add a logged in user value into a field placed in a CMS builder table from within the backend. Rather than work with an outside form, I would like to allow a user "author" access to a blog posting table and automatically place the user's name or num into a field hidden to all but admins. It does not appear that one can place $CURRENT_USER['num'] or <?php echo $CURRENT_USER['num'] ?> into a text field as a default value. I tried to make a field using the relatedRecords choice, using the accounts table and where clause:

num='<?php echo mysql_escape(@$CURRENT_USER['num']) ?>'

This does generate a field of values from the accounts table that the admin can see, but I don't know how one would pluck out a name or num value for use in a viewer for those records. For example, if the field is named "bloggers," the use of echo $record['bloggers.fullname'] just throws an error.

Any suggestions>

Thanks.