<form name="counter"><input type="text" size="8" name="d2"> - <input type="text" size="8" name="d3"></form> 

<script> 
<!-- 
// 
 var milisec=0 
 var seconds1=30
 var seconds2=300 
 document.counter.d2.value='30' 
  document.counter.d3.value='300' 
function display(){ 
 if (milisec<=0){ 
    milisec=9 
    seconds1+=1 
 } 
 if (seconds1<=-1){ 
    milisec=0 
    seconds1+=1 
 } 
 else 
    milisec+=1 
    document.counter.d2.value=seconds1+milisec
    document.counter.d3.value=seconds2+milisec     
    setTimeout("display()",100) 
} 
display() 
--> 
</script>