Introduce error message for a particular SAP standard function

Hi All,

In TCode CS02 - BOM Changes, for a particular BOM usuage [say D], whenever a user clicks on Material BOM- DELETE, I would like an error message to be displayed saying that they need a Change Number.

Could you please let me know how I go about acheiving this and in which module I have to build the code ?

Thank you,

Satish