Is it possible to use old values in a script?

Good question!

#If Not SCRIPTDEBUGGER
	Imports VI.DB.Compatibility
#End If

Public Function CCC_PreviousLastName(ByVal uidPerson As String) As String
	
	Dim person = Session.Source.Get("Person", uidPerson, EntityLoadType.ReadOnly)
	Dim histPerson As New VI.DB.History.ColumnHistory(person.CreateSingleDbObject(connection), "LastName",  Connection.LocalNow.AddDays(-100).ToUniversalTime)
	Dim previousLastName = histPerson.Changes.First.Changes _
   		.Where(Function(c) String.Equals(c.Columnname, "LastName", StringComparison.OrdinalIgnoreCase)) _
   		.Select(Function(c) DbVal.ConvertTo(Of String)(c.OldValue)).FirstOrDefault()

	Return(previousLastName)
End Function

VI.DB.History.ColumnHistory() still works with ISingleDbObject not with the "new" entitytype
Maybe there's better alternative that uses enitytype?

This would be my generic solution for an entity column's latest "old" value.

Public Function CCC_PreviousColumnValue(ByVal xObjectKey As String, columnName As String, Optional backTo As Date = Nothing) As String
    If String.IsNullOrWhiteSpace(xObjectKey) Then
        Throw New ArgumentNullException(NameOf(xObjectKey))
    End If
    If String.IsNullOrWhiteSpace(columnName) Then
        Throw New ArgumentNullException(NameOf(xObjectKey))
    End If

    Dim source = Session.Resolve(Of History.IHistorySource)()
    Dim columns = New List(Of String) From {columnName}

    Dim previousColumnValue = source.GetChanges(New DbObjectKey(xObjectKey), columns, backTo, History.HistoryMode.WithFkDisplays).
        OrderByDescending(Function(x) x.ChangeTime).FirstOrDefault?.GetOldValue(columnName)

    Return previousColumnValue
End Function