This message is sent to a dialog box's window function, to alter the control focus. The effect of this message is different than that of the SetFocus function because WM_NEXTDLGCTL modifies the border around the default button.
| Parameter | Description |
| wParam | If the lParam parameter is nonzero, the wParam parameter identifies the control that receives the focus. If lParam is zero, wParam is a flag that indicates whether the next or previous control with tab-stop style receives the focus. If wParam is zero, the next control receives the focus; otherwise, the previous control with tab-stop style receives the focus. | |
| lParam | Contains a flag that indicates how Windows uses the wParam parameter. If the lParam parameter is nonzero, wParam is a handle associated with the control that receives the focus; otherwise, wParam is a flag that indicates whether the next or previous control with tab-stop style receives the focus. |
Do not use the SendMessage function to send a WM_NEXTDLGCTL message if your application will concurrently process other messages that set the control focus. Use the PostMessage function instead.