Flip sketch origin about "Y" axis

I select a plane to sketch on (e.g. top), sketch opens.  I would like to actually sketch on the opposite side of the plane, as if rotating 180 degrees about the "Y" axis.  "Align Grid/Origin' will only allow me to select one of X-axis or Y-axis, but not both.  Suggestions?  SW 2009 64bit.

SolidworksSketching