Selectduplicates seems limited to one field

Could somebody please test this example from the Help wizard?

field LastName
field FirstName
selectduplicates LastName+", "+FirstName

In my databases, it takes no cognisance of the second field.

Yes, the current version of selectduplicates is busted - it turns out it is ignoring the formula! I just fixed it a few days ago, the fix will be in the next version.