> I do wish that I could use a programming editor that could look like a TeX output on the screen though ...

For other readers (I suspect you already know this), Mathematica and Sage (and other environments) do a pretty good job of providing TeX-like feedback on what you've just typed in (but not keystroke-by-keystroke, which would be nice).

For those unfamiliar with Sage:

http://www.sagemath.org/

My Sage tutorial:

http://arachnoid.com/sage