How to avoid duplicate entries using countif in Excel VBA

We can avoid duplicate entries in an Excel worksheet using the COUNTIF function in VBA. Here we have two choices: 1. We warn the user and delete the entry automatically or 2. We just warn the user and it is up to him to take any further action. Details available at: http://www.exceltrainingvideos.com/how-to-avoid-duplicate-entries-in-excel-using-countif-in-vba/