updateEditButtonState(ss);
	private void selectionChanged(SelectionChangedEvent event) {		ISelection s= event.getSelection();		if (! (s instanceof IStructuredSelection)) 			return;		IStructuredSelection ss= (IStructuredSelection) s;		if (ss.size() == 0){			fPreviewLabel.setText("");//$NON-NLS-1$			return;		}		NLSSubstitution first= (NLSSubstitution) ss.getFirstElement();		TextRegion region= first.value.getPosition();		fSourceViewer.setSelectedRange(region.getOffset(), region.getLength());		fSourceViewer.revealRange(region.getOffset(), region.getLength());		if (ss.size() == 1){			String message= NLSUIMessages.getFormattedString("ExternalizeWizardPage.preview", fPrefixField.getText() + first.key);//$NON-NLS-1$			fPreviewLabel.setText(message);		} else{			String message=  NLSUIMessages.getFormattedString("ExternalizeWizardPage.selected", String.valueOf(ss.size())); //$NON-NLS-1$			fPreviewLabel.setText(message);		}		}