XtRemoveAllCallbacks (widget, XmNactivateCallback);
XtAddCallback (widget, XmNactivateCallback, xm_generic_callback, instance);
XtRemoveAllCallbacks (widget, XmNvalueChangedCallback);
XtRemoveAllCallbacks (widget, XmNactivateCallback);
XtAddCallback (widget, XmNactivateCallback, xm_generic_callback, instance);
XtRemoveAllCallbacks (widget, XmNvalueChangedCallback);