Fórum CodigosnaWeb.com

<script type="text/javascript">
function muda() {
var largura = document.form.largura;
var alura = document.form.altura;
if(largura.value!="" && largura.value!="") {
document.getElementById('div').style.width=document.form.largura.value+"px";
document.getElementById('div').style.height=document.form.altura.value+"px";
}
}
</script>

<form name="form">
largura: <input type="text" name="largura" value="100" onkeyup="muda()">
<br>
largura: <input type="text" name="altura" value="100" onkeyup="muda()">
</form>

<div id="div" style="border:1px solid #cccccc; width:100px; height:100px;"></div>