Call a WebService from APM page (message box, logon page)

We have a lot of SSL v3 application that are using client certificate (from multiple CAs) for authentication and we would like to perform a call from our APM policy to perform OCSP validation (for multiple CAs).

We have the WS (.NET) and we would like to aumatically call it from an APM page (logon or message), send parameters to the WS and receive a response.

As someone already done some kinds of implementation? Is it possible to add some code into APM pages?

Thanks for your help