Implementing Drag-to-Submit Form

I am sick to death of assholes spammi开发者_JAVA百科ng my site, and I hate those stupid Captcha things, and my customers have had it up to their necks with the captcha on my site.

So, I had an idea. What if there was a small line. And all they had to do was simply drag a circle from the left of the line to the right. And once the circle reaches the drop-target (end of the line), the form will then submit. Sounds simple? No need to inconveniently type some random crap just to submit a form!

See demo pic:

Does anybody know how I would implement something like this? Can someone please help me? I need a little direction.

Thank you

That seems like a rather roundabout way of doing it, most spambots dont execute JavaScript in the first place, my solution would be to autofill a hidden field using javascript, or simply fill the action part of a form using javascript.