But, if HLOOKUP works for you then don't fix what ain't broke.
That's not the right attitude !
If you know there are likely to be issues down the line (as you outlined yourself), then better to swat the bug now rather than having to waste time finding the bug later and then fixing it.
Of course really he should be using a database rather than abusing an Excel spreadsheet as I've got doubts about his scalability... but that's another story
