* @param udf locator of user-defiend functions to resolve names of VBA and Add-In functions
* @return the external name or null
*/
public NameXPtg getNameXPtg(String name, int sheetRefIndex, UDFFinder udf) {
LinkTable lnk = getOrCreateLinkTable();
NameXPtg xptg = lnk.getNameXPtg(name, sheetRefIndex);
if(xptg == null && udf.findFunction(name) != null) {
// the name was not found in the list of external names
// check if the Workbook's UDFFinder is aware about it and register the name if it is
xptg = lnk.addNameXPtg(name);