Maintenance plan backup and reload the same database
Carlo,


  do you have other ideas?


You jus took a backup, so when you write the execute SQL Statement part of your job reference the MSDB backup history information tables to pull out the latest full and any other diffs/logs/etc that you would like to apply. The data can be found in msdb under the dbo schema and will give you the file names, etc, so there will be no need to pass anything and you can make it work should you want to do it from the last full or from the last full with the rest of the backup chain.

http://msdn.microsoft.com/en-us/library/ms188062.aspx