private void alterExistingConfigurationParameter(AddParameterDialog dialog,
TreeItem existingTreeItem) {
ConfigurationParameter existingCP = getCorrespondingModelParm(existingTreeItem);
ConfigurationParameter previousCP = existingCP;
previousCP = (ConfigurationParameter) previousCP.clone();
fillModelParm(dialog, existingCP);
fillParmItem(existingTreeItem, existingCP);
// the following may have changed in an existing param spec, that could
// affect the setting: