Your Diary is a message to every member of the board. When you want to draw attention to newly posted information, just edit the title of your very first post waaaaaaaaay back at the top of Page 1 of your PDA. you should let folks know which page they'll find the hot news on, too.
if you want to send a pm (Private Message) to more than one member, then i'm 99.99% sure you have to send it to each member separately.