How to manage "fields" in fckeditor

I'd like to use fckeditor to create email templates. In these templates I need to insert "fields". The values of these fields are computed when the email templates are used ie when the email is sent. These values depend on the context (date, to whom the email is sent, etc).
Internally (in the text) these fields will have a syntaxe like <$fieldname$> but I'd like to hide this syntax from the user and replace it with a more readable name with some visible attribute (eg: specific color or underline).
So my question is : What is the best and easiest way to implement such a system ?
Thanks in advance for your help.

pascal de oliveira
ramaplus