IUP - Obtaining the Ihandle in C from Lua

["Mark Meijer" <meijer78@...>]

Hi, I'm not sure if this is the right place for this question. If not, then 
I appologize. I was wondering how to hand my C code the Ihandle of an IUP 
element (in my case a regular dialog) that was created from within a lua 
script. I found the page in the manual (also in the new version, where it is 
found under System -> Guide > Other -> IupLua Advanced) mentioning  
lua_unboxpointer in (Lua 5), but I have no idea what is meant by this and 
there is no further explanation. I did a full text search for 
"lua_unboxpointer" in the lua sources as well as the IUP sources and got no 
hits, same when searching for just "unbox".

Does anyone know what I need? It also mentions lua_touserdata for lua 4, is 
this what I need for lua 5 then as well? If so, what exactly would I pass to 
the c function as argument, from the lua script, the dialog object itself?

Thanks.