Real beginners question

I have a datagrid that is used to insert values into a table. Beforethe insert occurs I want to be able to check that there are noidentical values already in the table. eg. I am inserting names, so amlooking for last name duplicates only.
If a duplicate is found, it should return an error message to the page.My question is, can I do this duplicate checking via SQL script ie. IFEXISTS etc... and have the error message returned from there, or do Ineed to grab a dataset of the table and look for duplicates before evengoing as far as the database with the new value to be inerted?
If the best approach is to catch the duplicate error after executingthe SQL script, how do I grab the error and return it to the page withthe datagrid? I'm sure this is pretty basic, but I am only just nowgetting into it.
SQL Server 2000 is being used here.
Thanks!

This was recently handled here, and a link to an article on AspAlliance was provided. It should help you too:

http://aspalliance.com/687