Dynamically modifying RetryInterval and FailureTimeout

Is it possible to dynamically adjust the RetryInterval andFailureTimeout settings in a BPL?

I've got a business process that calls a web service operation to get a session ID from an external system.  There is a string property returned in the body of the response that indicate an exception occurred in the external system. I have code in the BPL that examines the property and sets the status property to an error status when that occurs.

Depending on what the value is I want to adjust the RetryInterval and FailureTimeout values used in by the system when the ReplyCodeActions is set to E=RD.

Example: If the string is "No sessions currently available" I want to retry every 15 seconds for 10 minutes before disabling the process and raising an alert.

If instead the string is "System is down for nightly maintenance"  I want to retry every 5 minutes for 4 hours before disabling the process and raising an alert.

Suggestions?