I see You have a list in Column A of a couple hundred products. You want to easily add a sales rep to those hundred products.
If this is the case, type in the reps name next to the first product go in order. As you go the reps name will start to fill in as you type, just hit enter when the aouto fill starts their name.
The only other thing is if you have products you know that only one rep sells, then you could sort your items accordingly, then copy and paste the salesmans name next to those items.
If this is not what you are looking for, send a sample of the data. If you don't already have it, use Colo's HTML maker at the bottom of this page to send a sample.
Hope this Helps,
Michael