[development] How do I write to the database?

My colleague is trying to simply write to a mysql database. And having a pretty difficult time of it. He has gone through the forums, posts, books and Pro Dev Drupal and is still having a problem We are wondering if it is because he are working with computed fields? Does that make any difference in syntax, for example? If someone could post any samples they have used of syntax - writing to a Drupal 6.15, standard install using computed field values - we would be so grateful. If it works, send me your address - and I'll send you a $100.00 bucks in pure gratitude! Kind regards, Chana