Detect Blackberry Os Version?

Does somebody know the code to detect the Blackberry version with javascript? If its a blackberry i need to detect the version of the OS because our mobile site only support version 4.5.0.127 and up. If the version is under that i have to redirect the user to another page to tell him that his OS version is not supported, they have to update there OS before using our mobile site.

<script language=javascript>
<!--
if((navigator.userAgent.match(/blackberry/i)) && !request.getHeader("user-agent").matches("^BlackBerry[0-9]{0,6}/(4\. (5\.(0\.(1(2[7-9]|[3-9]{1}\d{1})|[2-9]{1}\d{2}){1}|[1-9]){1}|[6-9] |1[0-9]){1}|[5-9]|1[0-9]){1}.*") ) )
{
location.href='notcompatible.cfm';
}