Question about 'READBYME' property

We are using XMLForm and we've a problem with portal behaviour.

We want to create a ListShow form which displays only unreaded items in a folder.

Our problem is the following:

- When we use km navigation with a LayoutSet (ConsumerList) readbyme property is not activated until you open the file.

- However, when we have a km navigation iview using RenderListItem, every items are marked as readed when displayed (we display only property id of items). How can I avoid this?.

Thanks in advance.

Damiá