Set the webkit-keyframes from/to parameter with JavaScript

Yes, there is a way to do it dynamically with JavaScript. You can use css animation directives in native javascript code with the function Element.animate(). This approach is widely supported across browser, except for IE.

document.getElementById("tunnel").animate([
  // keyframes
  { transform: 'translateY(0px)' },
  { transform: 'translateY(-300px)' }
], {
  // timing options
  duration: 1000,
  iterations: Infinity
});

This function accepts two arguments - keyframes and options. Inside options you can specify the css animation parameters. Inside keyframes you can specify one or many transitional states. In your case with from and to you need two keyframes.