Removing white-space in item description

Summary

How can i detect white-space in item description

Content

How do I remove white-space from user defined item description using item rule I tried the match("//s", [Item].[Main].[Item Description]) function to validate and reject, but it yield no result.

Is there an other way to do it like to assign back the item description once the user have imputed the field? I mean to take the input from the user, trim it and assign it back to the item description?

Version

Oracle cloud application 19A