How To Backup A Database In Sql Server Management Studi Express Automatically

I come cross some post about how to backup a database in Sql Server Management Studio Express automatically. The scripts look like as below

USE [master]
GO
SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO
CREATE PROCEDURE [dbo].[sp_BackupDatabase]
@databaseName sysname
AS
BEGIN
SET NOCOUNT ON;
DECLARE @sqlCommand NVARCHAR(1000)
DECLARE @dateTime NVARCHAR(20)
SELECT @dateTime = REPLACE(CONVERT(VARCHAR, GETDATE(),111),'/','') +
REPLACE(CONVERT(VARCHAR, GETDATE(),108),':','')
SET @sqlCommand = 'BACKUP DATABASE ' + @databaseName +
' TO DISK = ''C:Backup' + @databaseName + '_Full_' + @dateTime + '.BAK'''

EXECUTE sp_executesql @sqlCommand
END



It throws that the DDL statement is not allowed. What's wrong with it?