Lisp program to delete duplicate entities

[Alphameric]

We have several drawings where a user (now departed) copied all entities in model space onto themselves. This means that the drawings are much larger than they should be, and editing the drawings is more dificult.

Does anyone know of a lisp routine which will cycle through the drawings in question and delete one of each duplicate items? I have done a Google search but so far have not found any.

Thanks

 

[Alphameric]

Thanks Paul. Unfortunately we don't have Express Tools but if it is the only answer maybe it is worth while purchasing.