Using http://clarius.codeplex.com/releases/view/6626 

Which then needs some text:

“The options deserve some more explanation besides being quite obvious:

  • Target blog: this is a dropdown that shows all the blog accounts you have currently registered in WLW. The “source” blog will always be the one you’re editing and publishing the current blog entry to.
  • Post summary: if checked, the cross-post will only contain the first 500 (200 is the default) characters of your current entry. ...

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