Is it possible to define the normal of a plane?

Why it matters?   A lot of times, I'll define a plane by a 3D sketch with a line and a point.   Then, I'll use that plane for making sketches and parts etc.    Later on, I need to re-define that original plane (as a part has changed).  When I do that, sometimes the normal of that plane 'flips' and all of my sketches are now on the other side of that plane and break, and it's just a huge mess.

Any ideas?

Sam