What is happening is that you are selecting one person from the list, clicking
Add, which puts that person in the list, you are then going back and selecting
a different person from the list, clicking Add, which clears the Add table, and
adds the second person.
Assuming you are working from the advanced button, what you should be doing, is
holding down the control key and selecting all the people you want from the
list, then clicking Add, to get all of the selected group into the Add list,
then click OK. Now you can go back with a different start of name, select
more, choose Add, and then OK, until you have all you want.
Hollis D. Paul [MVP - Outlook]
Mukilteo, WA USA