Finding duplicates in a column, prompt user then delete the current one

Hi there,

I would like to have few lines to code to let Excel first find duplicates against column 1 when users enter new record. If a duplicate is found, then a pop-up window saying duplicate is found or something like that and then have Excel delete the current line so that we don't have to manually delete it by right-clicking then hit "Delete".

The list goes on forever so I thought I should use a macro in worksheet change event, but i don' tknow how to get started.

Is this possible?

Please see the attached file.

Thank you