Every MAXScript editor window has an associated edit_window struct. This can be accessed using the GetWindowLong() windows API and the GWL_USERDATA constant as follows:
edit_window* ew = (edit_window*)GetWindowLong(hDlg, GWL_USERDATA);
This struct is defined in the file MAXScript SDK file maxscrpt/listener.h as follows:
struct edit_window
{
edit_window* next;
edit_window* prev;
Value* file_name;
BOOLneeds_save;
HWNDwindow;
HWNDedit_box;
intsr_offset;
intclick_tos;
intclick_at[CLICK_STACK_SIZE;
boolediting;
INT_PTRnew_rollout();
INT_PTRedit_rollout();
};