automatically initialize svnsync command from master server if slave is out of sync

I have a setup of master-slave SVN servers. Slave uses write through proxy, so every commit is forwarded to master.

When slave server is out of sync working copy checked out from slave repository can not be updated to the latest.

So I am looking for a solution that will automatically initialize svnsync command from master server if slave is out of sync while committing.

Thanks

[Updated] This situation occurs because we shut down our slave server at the end of the day, whereas master is up all the time. So if svnsync doesn't happen at slave startup, regular users must not face problems

However it has been long ago but just to close this for anyone facing this. Here is the setup I accomplished

1. Created a batch command to call svnsync from master to slave
2. Created a RDP service to call batch created in previous step on master svn server
3. User this service call on startup of slave machine with authentication.

So master slave sync is happening in two ways

1. When Slave machine startup it automatically calls this rdp service
2. Next commit automatically calls svnsync as it is in post-commit hook