For what purpose, exactly?
With CSS you can just use the :hover selector...
Something like:
Code:
.F9a div:hover
{
color: red;
}
That would basically turn any text in a div element within the .F9a parent class red.
So that should enable you to do whatever hover based effects you need.
If you DO actually need a class appending automatically on hover (again, why?) then that would require some custom jQuery/JavaScript and is therefore probably beyond the scope of this forum unless you find a developer who is familiar with jQuery and javascript.