Prendilo come esempio:
codice:
<SCRIPT LANGUAGE="JavaScript">
<!--
var old_vl='';
var new_vl='Stringa scorrevole ';
var tim_vl;
var obj_vl;
function start1(obj){
	if(!old_vl) {	
		old_vl=obj.value;
		obj.value=new_vl;
		obj_vl=obj;
		tim_vl=setInterval("start1(obj_vl)",500);
	} else {
		obj.value=(obj.value.substr(1)+obj.value.substr(0,1));
	}
}

function stop1(obj){
  if(tim_vl) clearInterval(tim_vl);
  obj.value=old_vl;
  old_vl='';
  obj.vl=null;
}
//-->
</SCRIPT>

<BODY>
<input type="button" value="Testo Fisso" onmouseout="stop1(this)" onmouseover="start1(this)" style="overflow: hidden; width: 100px;">
</BODY>
ciao