Client Authentication - Trusted Certificate Authority

I think it may be possible because this is in the client authentication description on F5.com.

The Request setting is often used in conjunction with iRules to provide selective access depending on the certificate presented. For example, this option would be useful if you would like to allow clients who present a certificate from the configured trusted CA to gain access to the application, while clients who do not provide the required certificate are redirected to a page that details the access requirements.

I would like the access requirements page to be the user name and password logon authentication page.