Public Function fn_HHMMSS(pDBeg#, pDEnd#) As String
Dim dHH#, dMM#, dSS#, dMS#
Dim lHH&, lMM&, lSS&, lMS&, lUB&
    
    dSS = (pDEnd - pDBeg) * 86400
    'dSS = 106404 / 25 ' for test purposes - critical test value
Stop
    dHH = (dSS / 3600)
    lHH = Int(dHH)
    
    dMM = (dSS - lHH * 3600) / 60
    lMM = Int(dMM)
    
    dSS = (dSS - lHH * 3600 - lMM * 60)
    lSS = Int(dSS)
    
    dMS = (dSS - lSS) * 1000
    lMS = fn_RndSch(dMS) ' school round
    
    lUB = 1000
    If Not (lMS < lUB) Then
        lMS = lMS - lUB
        lSS = lSS + 1
    End If
    
    lUB = 60
    If Not (lSS < lUB) Then
        lSS = lSS - lUB
        lMM = lMM + 1
    End If
    
    If Not (lMM < lUB) Then
        lMM = lMM - lUB
        lHH = lHH + 1
    End If
    
    fn_HHMMSS = Format(lHH, "00") & ":" & Format(lMM, "00") & ":" & Format(lSS, "00") & "." & Format(lMS, "000")
 
End Function