sends a BM_SETCHECK message to set the check state of a radio button or check box.
lResult = SendMessage( (HWND) hWndControl, // handle to destination control (UINT) BM_SETCHECK,(WPARAM) wParam,(LPARAM) lParam // = 0);
wParam
Specifies the check state. This parameter can be one of the following values.
BST_CHECKED
Sets the button state to checked.
BST_INDETERMINATE
Sets the button state to grayed, indicating an indeterminate state. Use this value only if the button has the BS_3STATE or BS_AUTO3STATE style.
BST_UNCHECKED
Sets the button state to cleared.
lParam
This parameter is not used.