information on how to implement syntax validation in a background thread

I am the author of the extension TextHighlighterExtension2012 and TextHighlighterExtension for VS 2010. Both extension provides color coding and syntax validation for JSON. But the syntax validation is executed on the main thread which not very good with large json file.

I am looking for information on how to implement syntax validation in a background thread.
What is the VS extensibility api to use for that.

Thanks

ftorres