check ssl server certificate on client side

The client connects via HTTPS to the BIG-IP. The BIG-IP also connects to the server via HTTPS. We want to ensure that the client (internet) has a valid certificate. The problem is, this specific application installed on the client is only capable to use a server certificate. On the BIG-IP, i think, it is only possible to require/request a client certifacte on the client side.