An application sends a BM_SETIMAGE message to associate a new image (icon or bitmap) with the button.
BM_SETIMAGE
wParam = (WPARAM) fImageType; // image-type flag
lParam = (LPARAM) (HANDLE) hImage; // handle to the image
IMAGE_BITMAP
IMAGE_ICON
The return value is a handle to the image previously associated with the button, if any; otherwise, it is NULL.
Windows NT: Requires version 4.0 or later.
Windows: Requires Windows 95 or later.
Windows CE: Unsupported.
Header: Declared in winuser.h.
Buttons Overview, Button Messages, BM_GETIMAGE