Complex sentence: Global BC will be debuting a new HD virtual set on September 27,2010, but HD newscasts launched along with "Global National with Dawna Friesen" on September 20, which will utilize the same set with minor changes to the desk.
Split into simpler sentences: Global BC will be debuting a new HD virtual set on September 27,2010. This will happen one week after the launch of "Global National with Dawna Friesen", which will utilize the same set with minor changes to the desk.