MaxMorais

// add a trigger on field "custom_field1"
cur_frm.cscript.custom_field1 = function(doc, cdt, cdn) {
  // update a new field "custom_field3"
  doc.custom_field3 = flt(doc.custom_field1)*flt(doc.custom_field2)/1000; 

  // refresh in form
  refresh_field('custom_field3');
}