Moin,
As per http://www.sqlservercentral.com/scripts/Backup/62497/ try it:-
From this you can get a pretty good idea of how fast your database is growing.
select
BackupDate = convert(varchar(10),backup_start_date, 111)
,SizeInGigs=floor( backup_size/1024000000)
from msdb..backupset
where
database_name = 'DatabaseName'
and type = 'd'
order by
backup_start_date desc
HTH!
Manu