Using assystETM to process an email to log against a Custom Form

Has anybody out there built an assystETM channel which will process an email and log a new ticket using a specific Custom Form?

If so I could do with some guidance as to how you reference the specific Custom Form you want to use.

We will be looking at taking the data out of the body of the email to populate the custom fields within the custom form which I am comfortable with, I am just struggling with how to call that custom form.