This is the script I've recently started using for backing up my SQL database.

declare @datetimestamp varchar(15) 
declare @bu_command varchar(4000)
declare @del_command varchar(4000)
declare @filename varchar(255)
declare @archive varchar(255)
declare @result int

set @datetimestamp = 
	substring(convert(varchar(32), getdate() ,120),1,4) 
	+ '-' + substring(convert(varchar(32), getdate() ,120),6,2) 
	+ '-' +  substring(convert(varchar(32), getdate() ,120),9,2) 
	+ '_' + substring(convert(varchar(32), getdate() ,120),12,2) 
	+ substring(convert(varchar(32), getdate() ,120),15,2) 
	+ '_' + substring(convert(varchar(32), getdate() ,120),18,2)
	

set @filename = 'c:\Backups\xfire_' + @datetimestamp + '.bak'
set @archive   = 'c:\backups\xfire_' + @datetimestamp + '.7z' 

BACKUP DATABASE xfire  TO DISK = @filename

set @bu_command = 'c:\7za.exe a -t7z ' + @archive + ' ' + @filename 
set @del_command = 'del ' + @filename

exec @result = master..xp_cmdshell @bu_command

if (@result = 0) 
	begin
	exec @result = master..xp_cmdshell @del_command
	end
else raiserror ('7Zip error', 1, 1)