The FOX GUI has exactly this capability, you can connect a variable directly to the widget, without requiring any glue code at all. In fact, you can connect the same variable to multiple widgets at the same time (eg a 'spinner' widget and an 'editeline'), without requiring the programmer to write any type of callback mechanism.
This works because all GUI events are bi-directional. For more information, read: http://www.fox-toolkit.org/datatarget.html
That seems a lot of code, compared to: http://www.torjo.com/win32gui/save_dlg.html Not to say about validation... Best, John -- John Torjo, Contributing editor, C/C++ Users Journal -- "Win32 GUI Generics" -- generics & GUI do mix, after all -- http://www.torjo.com/win32gui/ -- v1.5 - tooltips at your fingertips (work for menus too!) + bitmap buttons (work for MessageBox too!) + tab dialogs, hyper links, lite html