ADFS , Custom Auth using URL Redirect

Hi,

I am new to ADFS. Need help in checking if the following is possible with ADFS 2.0..
I have a custom authentication setup hosted on a web server. Currently the ADFS is configured to authenticate with AD. I would like to have my custom authentication also done as part of the ADFS authentication process. I mean the flow should be:

1. User authenticates using AD credentials
2. There should be a redirect from ADFS to my webserver which will complete its authentication and returns success/failure back to ADFS
3. Depending on the success/failure received by ADFS, it continues or halts the authentication process. .

Any pointers for how to configure the ADFS to do the above would be of great help.. 

Thanks