final TextBox defaultValue = new TextBox();
final DTCellValue52 dcv = at.getDefaultValue();
defaultValue.setStyleName( "form-field" );
defaultValue.setText( (dcv == null ? "" : dcv.getStringValue()) );
defaultValue.setEnabled( !isReadOnly );
defaultValue.addChangeHandler( new ChangeHandler() {
public void onChange(ChangeEvent event) {
at.setDefaultValue( new DTCellValue52( defaultValue.getText() ) );
}
} );