You can use .chinfo to add a greet message to an user (channel specific or not) and do .chanset #channel +greet to activate the display of the userinfo on #channel
first you need to determine who is the channel owner is that someone who gets ~ prefixed (on some ircds) after he joins channel or is that the one who is owner of the eggdrop if its the latter CrazyCat's code will work fine for that if its the first u will need something else.
let me ask you on what network are you using this ?