Restrict the user to edit particular records if the other user is editing them in SQL Server

Hi

Can any one give me an idea about how to restrict the other user if one works on the particular record.

Let me say i am having a table with the name tblProduct and i used to edit the records from the code behind using my website.

When one user login into the site and  search for the particular products and edits the product and at the same time other user log in and try to edit the same product, i need to show the alert message, "the user (username) is already working on this. please wait for a while."

Hope this is very clear.

I know here i need to implement some logic over here.

Can any one give me an idea about how to achieve this,

Please let me know if this is not clear.

thanks