To configure Multiple Exchange 2007 client access server with load balancer we need to Offload Certificate to the load balancer.
Offloading Certificate is the process where we uploaded certificate into the load balancer and this box will accept the request and decrypt the certificate and it will create a new session from the load balancer to the exchange servers. This is called SSL termination where SSL Session from the client is terminated at the LB and new session is created between the Server and Load Balancer
To configure SSL offloading for Outlook Web Access, you must perform the following procedure on each of your Client Access servers. Below is the link which gives the details description on configuring Client Access Servers
Below link on F5 Load balancer which has details description on how to configure for Exchange 2007 Client Access server for OWA, Active Sync, Pop3, IMAP etc