Exchange VSS backup - using CHKSGFILES API for database cosistecy check

Hi
Working on VSS Backup Application for Exchange 2010 , try to perform database and log file  verification befor calling  VSSAPI - BackupComplete (as recomended in docs for VSS Exchange from Exchnage 2010 backup and restore SDK )

Try to do verification  with use of CHKSGFILES API


Is the calling sequence  right for CHKSGFILES API ?


................

VSS API call  IVssBackupComponents::DoSnapshotSet

CHKSGFILES API calls for verification

VSS API call  IVssBackupComponents::BackupComplete

..............




  CHKSGFILES API calls for verification  that I do in details :

1.  ErrInit     - successfull
2.  ErrCheckDbHeaders" - get errFileAccessDenied  (Cannot access file because it is locked or in use)

Application  has  "SeBackupPrivilege"  NT Defined Privileges 

The other question - how to get  the number of pages in database to verify (this value is needed to call  ErrCheckDbPages function )

Is any examples how to use CHKSGFILES API ?

Thanks