Unisntall Service Pack (sp3) for SQL Server 2008 R2 using commandline script

Hi,

How can we un-install Seevice Pack(sp3) for SQL Server 2008 R2 EE SP3 usingcommandline option.

Can anyone give  the script to unstall service pack for SQL Server 2008 R2 SP3 using commandline script?

Note: We know how to un-install manually.

Thanks