var aaa=abs(parseInt(document.form1.aaa.value));
var bbb=abs(parseInt(document.form1.bbb.value));
document.form1.ccc.value = aaa/bbb+1;
var bbb=abs(parseInt(document.form1.bbb.value));
document.form1.ccc.value = aaa/bbb+1;
=>
document.form1.ccc.value = Math.abs(aaa/bbb)+1;