Oh the dreaded mans balls itching. I know how you feel.
What you should do is wash your balls and groin really good daily and dry the area out after you shower or wash down there.
Also change your underwear or boxers daily if you don't do so to help keep the area around your groin clean and healthy.
I also find that if I put some baby powder in my underwear it helps prevent sweating down there and stops my balls from itching.
Applying some medicated powder or other Fungal cream to your balls can also help stop the itching of your balls.
Also wear loose fitting boxers or underwear when your balls itch to avoid chafing.