JournaVouchers doesn't works!

I do this:

If (BoJV Is Nothing) Then

Set BoJV = Company.GetBusinessObject(oJournalVouchers)

End If

With BoJV.JournalEntries

.SetCurrentLine (0)

.Lines.Add

.Lines.AccountCode = "61200001"

Calculos

.Lines.Debit = Debito

.Lines.Add

.Lines.AccountCode = AccountCode

.Lines.Credit = Credito

.Lines.Add

Res=.Add

End With

When doing .Add, variable Res get the value=0, but when i go to see the results in SAP, no new journal vouchers are created. Where can be the problem? I've read that journalvocheurs.JournalEntries.lines.ShortName is a mandatory field, but i don't know where to get this value and if it can be the problem, but SAP doesn't gives me any error, the result of add is OK(0) and i don't use this suppossed mandatory field.

Thanks!