IP Pools Question

Good Evening We have FreeRadius 3.0.20 running here quite happily - but have a very small issue we' like some help with Some of our connections use ippools (running from a mssql server) As a general rule this works exactly as it should Very occasionally the sql server will time out - maybe once or twice a day due to transactions clashing When this happens the session comes on-line but is not issued a IP. What I'd ideally like to do is simply reject that connection IF that happens which will force the router to log in again - it will then get an IP and will be happy Is there an easy way to catch this and reject the connection (or even re-try the ippool module) ? Thanks in advance Richard