I have read through dozens of posts about Duplicates but cannot find this question answered.

When entering a record I would like the database to check a particular field for duplicates (not the key field) and if a duplicate is found I would like it to display a warning, e.g. This Serial Number / Telephone Number is already in the database. Are you sure you wish to add this entry? Then if Yes - add entry, if No, return to Add page.

Hope someone can help with this!

PS I have successfully added the bit of script which rejects duplicates in the field out of hand, and that works fine.