change the default response from "Send the response now" to "Don't send a response" on the dialog box presented when a user accepts an invitation to a meeting generated from Calendar in Outlook 2003.

We run Win 2K3 SBS Premium with Exchange 2003 SP2, a Win2K3 Std file server & 3 x Win 2K3 Std terminal servers. Users run Outlook 2003 only thru their TS sessions. When someone schedules a meeting using Calendar & Invites Attendees, we have a lot of users click on the OK button with the default "Send the response now" radio button pre-selected. This generates a lot of unnecessary traffic & requires double handling to delete the message when returned to the Meeting planner. Is there a way to change the default from "Send the response" to "Don't send the response", ideally using GP or a registry key?
We use the Calendar to advise the team of staff movements, system maintenance etc, as well as actual meetings and don't require acknowledgement for +75% of meetings or calendar events. I know I can set up a Rule in Outlook to auto-delete these responses, but we would probably need to see the responses to the other 25% of the messages. Thanks in advance for the help.