Updating an Instance List Item

First get the dataitem for the instance list entry.
To get the first entry in the list you can use the DataItemsbyUII collection:

Define_Com Class(#VF_LM003O) Name(#MyDataItem) Reference(*DYNAMIC)
#MyDataItem <= #avListManager.DataItemsbyUII<1>

To get an instance list entry using the AKeys and NKeys use the GetFromList method:

Define_Com Class(#VF_LM003O) Name(#MyDataItem) Reference(*DYNAMIC)

#avListManager.GetfromList Akey1('102033') Dataitem(#MyDataItem)

Then update the instance list entry using the following (the selected and current statuses and any other values):
#MyDataItem.avIsSelected := True

#MyDataItem.avIsCurrent := True

#MyDataItem.avAColumn1 := 'Updated value'

#MyDataItem.avUpdateDisplay

To show the default command, use:

#MyDataItem.avExecuteDefaultCommand

Where the default command is the command the user was last using. If no command is currently in use, or the command being used is defined in the business object as Default=Never, then the business object's default command will be used.

You cannot update the items keys avAKey1 -> avAKey5 and   avNKey1 -> avNKey5. 

Never keep list item references in your own code because your application will leak.