Weld vertices by normal orientation


I am looking for a script that will weld all vertices of an Edit-Poly object, if they share the position and the same vertex normal orientation.

To have it as a separate window with a button to press would be nice.

I my self know nothing about programming what so ever... so thanks in advance!

I have a model where all the objects only consist out of loose, no welded polygons inside. On top of that there is a second inverted polygon for each normal one.
So welding the vertices will weld some of the correct and some of the inverted polygons and the model will be unusable.