I managed to work around it using JavaScript, so this question is resolved. Here's what I did for future reference: Add a Javascript Extension object to the Main.EventCalendar function changeTextHol() { var textboxObject = document.getElementById('XWiki.CalendarEvent_user'); textboxObject.value = "<h5>Holiday</h5> "; } function changeTextOpe() { var textboxObject = document.getElementById('XWiki.CalendarEvent_user'); textboxObject.value = "<h6>Operation</h6> "; } Add these lines to XWiki.CalendarSheet but not between the set of <dl> tags. <dt class="label"><label>$msg.get("Category"):</label></dt> <td><input id="changeTextHol" name="cat" type="radio" onclick="return changeTextHol()" /> <h5>Holiday</h5><br /></td> <td><input id="changeTextOpe" name="cat" type="radio" onclick="return changeTextOpe()" /> <h6>Operation</h6></td> Cheers -- View this message in context: http://xwiki.475771.n2.nabble.com/Adding-the-category-object-to-the-calendar... Sent from the XWiki- Users mailing list archive at Nabble.com.