you don't need, because you check it also in the function + it's an endless loop so it is enough if you just call the function:

Code:

---

function Rotate_me()
{
	while (1)
	{
		if (key_a)
		{
			my.pan += 2 * time_step; 
		}
		wait (1);
	}
} 

action rotate ()
{
	Rotate_Me();
}

---