how do i add a metatable to a table in C?

["Paulo Lopes" <pmlopes@...>]

static int access_intvar (lua_State *L)
{
	int *var = (int *) lua_topointer(L, lua_upvalueindex(1));
	if(lua_gettop(L) == 0) {
		lua_pushnumber(L, *var);
		return 1;
	} else {
		*var = luaL_checkint(L, 1);
		return 0;
	}
}

int main()
{
	lua_State *L = lua_open();
	luaL_openlibs(L);
	
	int foo = 100;
	
	lua_newtable(L);
	
	lua_pushstring(L, "foo");
	lua_pushlightuserdata(L, &foo);
	lua_pushcclosure(L, access_intvar, 1);
	lua_settable(L, -3);
	
	lua_setglobal(L, "global");

	// main execution
    if(luaL_dofile(L, "test.lua") != 0)
	{
		printf("%s\n", lua_tostring(L, -1));
		lua_pop(L, 1);
	}
	
    lua_close(L);
	return 0;
}

I'd like to add some metatable to the main "global" table in order to
call the cclosure just by:

global.foo = value and x = global.foo

right now it works if i call like: global.foo(value) and x = global.foo()

i want to map __index and __newindex functions to the closure but i'm
a bit confused on how to make it.