Wait, I am not really sure what you're asking for. Are they going to install the script? if so whats the email of the bot going to be and you do know for the conversation to close on both sides then both of you will need it installed, or something like this.
jscript code:
function OnEvent_ChatWndReceiveMessage(ChatWnd, Origin, Message, MsgKind) {
if (Origin !== Messenger.MyName) {
if (Message =="-1") {
ChatWnd.SendMessage("/close")
return ''
}
}
}