Enforce chosing from products options

[Wizard]

Hello,

 

I'm trying to enforce my customers to chose an option from the products options drop down menu that is in the product_info.php file.

Anyone knows how to do it using javascript? I've tried a few different ways but it just doesn't seem to work.

The option that users will see wil be something like a line saying "chose option", and if they do not choase a differnt option from the drop down menu then the javascript will bring a pop-up will a message.

 

 

 

Thanks!