It appears it is only possible to use an IP address when creating match conditions in a class map which makes sense. 

We are using this basically as a NAT.

ie, server sends an HTTP message to the ACE containing XML

ACE then encrypts with an SSL cert and substitutes a public IP address and sends the XML out to a customer IP on the public internet

Problem is when customer changes the IP address, we need to change the configuration on the ACE.  Ideally if I could use a DNS name, then the customer can manage any changes via DNS and not involve us.

Disclaimer: I'm a complete novice to the ACE

Any ideas appreciated!