Hola paloclanweb!
<script language="javascript" type="text/javascript">
function soloNumeros(){
var numero = window.event.keyCode;
if (numero < 48 || numero > 57){
window.event.keyCode = 0;
}
}
}
</script>
<input name="txt_idEjec" type="text" size="10" onKeyPress="soloNumeros()">
espero te sirva
salu2.-
