Lisp in toolbar command for toggling a layer state?

Hello,

I'm pretty green when it comes to lisp, even though I've been using AutoCAD
for 8 years. It's something I've always wanted to learn but I have never
taken the time.

One thing I would love to find out is how to write a simple toolbar command
lisp expression to toggle the state of a layer with a fixed name (for
example "Viewports" which appears in nearly every single drawing). Right
now I have 2 buttons, one that turns it on, and the other off. This is OK,
however now I'm faced with a huge project in which there are several x-ref
layers over multiple drawings that I'd love to be able to turn on and off,
without creating 2 buttons for each one.

Does this make sense? I think it's something about querying the layer state
and turning on or off with what the query returns, but I'm not sure how to
write that in lisp. I have some javascript and C++ exprience, so the logic
is simple, but the syntax is beyond me, and searching through the help
didn't help me (pun intended).

Thanks for any help,
Nathan

 

Hmm... ok, well, can someone just shed some light on how I would query a
layer's state using autolisp? I can probably figure out how to get the if
statement working, and controlling the layer's state is easy.

Thanks in advance,
Nathan