Sources confirmed Monday that Walter and Nancy Brandt, grandparents of Boston-area systems consultant Charles Brandt, 31, still do not have the slightest idea what their grandson does for a living. 'We are very proud of our Charles,' said Nancy, 82. 'Whatever he does in that job of his, I'm sure it's very impressive.' Said Walter: 'I think what Charles does is make sure companies have enough computers and employees so that they canoh, I haven't a clue.' The couple also has no idea what their granddaughter, Erica Haselrig, a Lodi, NJ, human-resources supervisor, does for a living. 