Perpendicular surface along midpoint of existing surface

Hi all,

Is there a way to create a surface that would be at the middle of a surface (referencing two edges of the surface) and also perpendicular to it?  For example, if I had a flat surface that was 6mm wide, I could create a perpendicular, ruled surface along one edge and then offset it by 3mm, but what if the surface varied in width.  Trying to do this without sketching.

Thanks!

SolidworksSurfacing