UDF (user defined function) replacement for Excel's DATEDIF function

[snb]

Rick,

Wouldn't this be an alternative ?
Interval can be "y","m","d", or "yy","mm","dd"

Function xlDATEDIF(ByVal StartDate As Date, ByVal EndDate As Date, Interval As String) As Variant
  If StartDate > EndDate Then
    Err.Raise 5
    Exit Function
  End If
   
   If Len(Interval) = 1 Then
        xlDATEDIF = Choose(InStr("YMD", Interval), Year(EndDate) - Year(StartDate), DateDiff("m", StartDate, EndDate), EndDate - StartDate)
   Else
        NumOfYears = Year(EndDate) - Year(StartDate) - IIf(100 * Month(StartDate) + Day(StartDate) > 100 * Month(EndDate) + Day(EndDate), 1, 0)
        NumOfMonths = DateDiff("m", StartDate, EndDate) - IIf(Day(StartDate) > Day(EndDate), 1, 0)
        DaysDiff = EndDate - StartDate - IIf(Format(StartDate, ",0000") * 1 > Format(EndDate, ",0000") * 1, 1, 0)
        
        xlDATEDIF = Choose(InStr("YMD", Right(Interval, 1)), NumOfYears, NumOfMonths, daysdiff)
  End If
End Function

[Rick Rothstein]

Function xlDATEDIF(ByVal StartDate As Date, ByVal EndDate As Date, Interval As String) As Variant
  If StartDate > EndDate Then
    Err.Raise 5
    Exit Function
  End If
   
   If Len(Interval) = 1 Then
        xlDATEDIF = Choose(InStr("YMD", Interval), Year(EndDate) - Year(StartDate), DateDiff("m", StartDate, EndDate), EndDate - StartDate)
   Else
        NumOfYears = Year(EndDate) - Year(StartDate) - IIf(100 * Month(StartDate) + Day(StartDate) > 100 * Month(EndDate) + Day(EndDate), 1, 0)
        NumOfMonths = DateDiff("m", StartDate, EndDate) - IIf(Day(StartDate) > Day(EndDate), 1, 0)
        DaysDiff = EndDate - StartDate - IIf(Format(StartDate, ",0000") * 1 > Format(EndDate, ",0000") * 1, 1, 0)
        
        xlDATEDIF = Choose(InStr("YMD", Right(Interval, 1)), NumOfYears, NumOfMonths, dasdiff)
  End If
End Function

I haven't gone through you code yet, but is the text I highlighted in red a typo for DaysDiff?