>
> Sure.  Say, maybe you could start the expression with an open
> parenthesis and evaluate it when you see a return
> following the matching right parenthesis :-)
>

Another way to do it, although annoying for the laptop users, is the
Mathematica way of <RET> being CR and <ENTER> being Eval.  Another
system I have used...MPW?...gave a different way based on <RET> and
<Cmd>-<RET>. In Emacs, it's C-j, or C-x C-e if you don't want a
result.

-John