ok. so ive tried about a million different things, and i just cant seem to get this to work how i want. it seems trival at first, and ive got a handful of partially working versions but everytime i run into some kind of problem that usually ends with the project freezing or breaking.
simply, i want this: 
to look like this: 
now ive got a so-so technically working-how-its-supposed-to version, 
, but i want the ring slot to be in the block itself, without the ring parameters because i am already defining the parameters i want to use to the left.
heres some examples.
this, is all good:
acts just like a ring
heres where things get tricky:
nothing out of the ordinary, returns the unevaluated expression, but
it gives me the name of the wrong upvar
heres the code of what ive got;
(ive gotten close a couple of times without js using join / split blocks but they started acting up and getting too complicated for theyre supposed to do)
but i want 
instead of 
and ideally, i want to be able to have
with a multi arg(which i could handle if the main block would behave) that still does all of the steps but doesnt nest into oblivion.
this is what i currently have:
which is just tne most stable thing ive got right now.
this 
explaination
(which is a ring, with the 'a' var not in the slot but taking place of the slot, so it doesnt just ring the a variable, but evaluates it into the expression that was put into the custom block and puts that into the ring, and the input list lets me set the parameter names to whatever was set by the upvar, as a string) (basically im returning a ring with the custom block vars passed in as the right values)
actually works great until i try constructing 
, and has a tendency to bug out and freeze snap if its part of an error
basically i want to know how rings declare parameters and how they become available in the right scope.