create a new expression for a live template for actionscript

I'm working in actionscript, love macros that let me create trace statements and so far I have one that gives me:

Logger.log(className:methodName);

which is great. this uses the epressions found in the edit variables window, via the expressions dropdown, eg jsMethodName()

but now I want to add an expression that lets me list the params that any given method takes and their values

this exists for java, I believe, or groovy, but not for actionscript, so I guess I have to write it myself

first question: has anybody already done this already?

second question: if not, where does the source for, eg, jsMethodName() live? if I could look at that I could probably figure out my new expression from that

other tips? thanks