SQL 2005 Deattach database and attach a new one with same name

I need some help to script and schedule some tasks to do in sql 2005. I have One database to be backed up full and I need back the space used by this database. Manually I do the deattach of the database (I don´t need to keep the connections to the database because its a backup database) Then I compress this both files (mdf and ldf) and finally it´s sended to the respective folder. I have one database template with the same data (purged) of this database with the minimum space. (2048kb) I attach this file and the database it`s online again. I want to do this process (all of them) by a scheduled task in a script to do all. If I need to write sqlcmd or windows schedule process I have no problem. I dont want to use the full backup and clear the old backups of the dbms because I dont have the way in SQL 2005 to compress the old data and get a new database clear.

Thank you in advance.