A new tool for helping site owners with structured markup for events has appeared recently in Google Webmaster Tools.
The interface for this new tool called the ‘Data Highlighter’ is shown below:

At the moment the tool is restricted to Events markup, and the video shows you how to set about Highlighting.
On selecting the ‘Start Highlighting’ option, you get the following screen:

All you need to do is enter the URL of the page containing events to start with. This looks to be the start of a move by Google to make decorating html and adding schema somewhat easier than relying on development cycles. As we move into 2013, the data highlighter tool is likely to become much more comprehensive.