Rsync error with outlook data pst file

Hi,

I am using and automated script that backs up 3 windows Pc’s on the network but recently I have been having trouble with the backup due to the outlook data pst file. I get the error:

2014-11-19 09:31:54 +0000: Run Shell Script failed - 1 error
2014-11-19 09:31:54 +0000: rsync: read errors mapping "/Volumes/Users/***/Documents/Outlook Files/My Outlook Data File(1).pst": Input/output error (5)
rsync: read errors mapping "/Volumes/Users/***/Documents/Outlook Files/My Outlook Data File(1).pst": Input/output error (5)
ERROR: Documents/Outlook Files/My Outlook Data File(1).pst failed verification -- update discarded.
rsync error: some files could not be transferred (code 23) at /SourceCache/rsync/rsync-45/rsync/main.c(992) [sender=2.6.9] (23)

I am able to solve the problem by closing down outlook on the computer the error occurs on but this is a bit of a pain because I am never sure if the error will pop up again as it can run normally sometimes and others not.

I currently use the code:

rsync -va --update "/Volumes/Users/***/Documents" "/Volumes/BAckup Array/***/"

is there anyway of avoiding the outlook data pst file at all?

It would be a great help if there is.

Thanks,
Bruce