function buttonclick(formfield,correct,number)
{
   var rightlayer = "right"+number;
   var wronglayer = "wrong"+number;
   var answer = 0;
   
   for(x=0;x<=4;x++)
   {
      if(formfield[x].checked == true)
      {
         answer = formfield[x].value;
         break;
      }
   }
   
   // check an answer has been selected
    
   if(answer == 0)
   {
      return;
   }
  
   // display the appropriate response

   if(document.layers)
   {
      if(answer == correct)
      {
         document.layers[rightlayer].visibility="show";
         document.layers[wronglayer].visibility="hidden";
      }
      else
      {     
         document.layers[rightlayer].visibility="hidden";
         document.layers[wronglayer].visibility="show";
      }
   }
   else  if (document.all)
   {
      if(answer == correct)
      {
         document.all[rightlayer].style.visibility="visible";
         document.all[wronglayer].style.visibility="hidden";
      }
      else
      {
         document.all[rightlayer].style.visibility="hidden";
         document.all[wronglayer].style.visibility="visible";
      }
   }
   else
   {
      if (answer == correct)
      {
         document.getElementById(rightlayer).style.visibility="visible";
         document.getElementById(wronglayer).style.visibility="hidden";
      }
      else
      {
         document.getElementById(rightlayer).style.visibility="hidden";
         document.getElementById(wronglayer).style.visibility="visible";
      }
   }
}