Unfortunately, there's not a feature or a function for this right now. I know it's been requested; I requested it myself.
Windows Live Writer is most likely going to be released 3rd quarter this year and we can only hope something like this will be in it.
Don't bet your life on it.
Windows Live Writer developers have given, nor provided any insight in to what's going to be in the next release.
I hope this helps...
Later,
Larry