Can I enact a non-competition agreement with a 1099 contractor?

I am in the process of getting ready to hire a commission-only salesperson (1099 employee) for my business, but I am having a difficult time understanding whether or not I can enact and enforce a non-competition agreement.

It sounds as though a court would uphold a non-competition agreement for a reasonable period of time (I'm leaning towards 2-3 years) following the end of an employer/employee relationship, but am uncertain on whether or not it could legally include new client relationships formed during their employment when they would be the primary cause of creating new client relationships.

As an asset that is clearly worth protecting via some sort of non-competition agreement (properly limited in scope by geography, duration, and established client base), wouldn't all existing clients at the time of employer/employee relationship termination be covered by the non-competition agreement, even if they were not clients prior to the employees employment and the client relationship is a direct result of the employees work?