I develop a meeting management system. I would like to start the meeting via a custom Outlook plugin. So I developed a plugin to save the meeting into my web application and Outlook. Besides, I would like to collect the meeting request responses via this plugin. I added three custom buttons into the ribbon for Accept, Reject, Tentative events instead of their default button. If the meeting has custom user property which specified to send by custom form, I hide the default buttons and show the custom button in the ribbon. But the default buttons are in the reading pane. I can not change the visibility of those buttons in the reading pane. I tried some of the other methods to achieve this like below.
1- I tried to handle the ItemSend event. If the received message is a MeetingItem, I checked what the response is.
2- I tried to access the Actions of MeetingItem and change the enable status of those Actions. But The MeetingItem has Reply, Reply to All and Forward actions. There were not the actions Accept, Reject or Tentative.
3- I checked the InlineResponse and InlineResponseClose events. Although there is an event description in which the event will fire when the user sends the inline response in the documentation page(https://docs.microsoft.com/en-us/office/vba/api/outlook.explorer.inlineresponseclose), the event has not been fired.
4- I tried to access the ReadingPange objects of the Panes of ActiveExplorer. While I am debugging the code, the visual studio redirects to me the outlook interface, as if it can not read the line.
5- I tried to change the flow of the app. I sent a MailItem instead of MeetingItem to the Attendees. But I created a MeetingItem and saved it to the calendar of the requestor as well as I sent the MeetingItem with MaillItem as UserProperty which is a type of Outlook.OlUserPropertyType.olOutlookInternal. But it gives the error as "This type is not supported" while debugging.
Please let me know what I can do or if you have any other suggestions for this.