Public Function MonthDiff(DateBeg As Date, DateEnd As Date)
  Dim ret As Long
  Dim d1, d2 As Date
  
  If IsNull(DateBeg) Or IsNull(DateEnd) Then
    MonthDiff = Null
    Exit Function
  End If
  
  If DateBeg < DateEnd Then
    d1 = DateBeg
    d2 = DateEnd
  Else
    d1 = DateEnd
    d2 = DateBeg
  End If
  
  ret = (Year(d2) - Year(d1)) *  12  + (Month(d2) - Month(d1))
  If ret <>  0  And Day(d2) < Day(d1) Then ret = ret -  1 
        
  If d1 = DateBeg Then MonthDiff = ret Else MonthDiff = -ret
End Function