The database doesn’t scan. The program scans, and adds it to the database.
However, to add this functionality, you do need some pretty decent programming skills. Even more difficult when you want to “add” this functionality to an already existing program which is not yours.
Next to that, another way is to write something which has nothing to do with Gallery. Something that only scans a certain dir and adds new files to a database. Like the post above suggested, this little program could be entered into a cronjob to be run automatically by your system under a time interval. (each hour, each day, etc)
I must say, a single program that scans a dir and adds new files to the db, should be pretty easy. Even for a beginner. Google for it. 🙂