SQL Svr 2000: Replicate table structure

Fairly new to SQL, all OJT. Need to come up with the best method of updating customer databases with table structure changes that have been made in an application. Already have a method of generating a script that will add any new columns to their tables for any columns added in the master database, but can’t figure out the best way of updating other table structure changes such as size, type or allow nulls. Thanks in advance