T-SQL??

something along the lines of

restore database [thesecondarydb] from disk =

'C:\Program Files\Microsoft SQL Server\MSSQL11.MSSQLSERVER\MSSQL\Backup\primarydb_diff_backup.bak'

with move 'logicalname' to 'C:\Program Files\Microsoft SQL Server\MSSQL11.MSSQLSERVER\MSSQL\DATA\secondarydb_datafile.mdf',

move 'logicalname' to 'C:\Program Files\Microsoft SQL Server\MSSQL11.MSSQLSERVER\MSSQL\DATA\secondarydb_logfile.ldf'

, replace, norecovery