Quickly remove Objects on Block with swept selected object, but can not undo when a mistake select Object

[Mountain_XD]

This is a lisp use remove Object on Block but When I make a mistake select Object  i can not undo. Somebody Help me this problem. Thank you so much !

Here code : 

 

EraseObjectFromBlock.LSP

[Emmanuel Delay]

Have you tied:

Undo, then REGEN.

 

It seems like without a REGEN it appears like undu isn't working.

Is that good enough of an answer?