function getCMB() { var L=document.getElementById("L"); var W=document.getElementById("W"); var H=document.getElementByid("H"); var CMB=document.getElementByid("CMB"); if(typeof(eval(L))=="object" && typeof(eval(W))=="object" && typeof(eval(H))=="object") { CMB.value=parseFloat(L.value) * parseFloat(W.value)*parseFloat(H.value); } }