Tener dos submit

[chalchis]

function cForm(form){
var winl = (screen.width - 650) / 2;
var wint = (screen.height - 500) / 2;
winprops = 'height=500,width=650,top='+wint+',left='+winl+',s crollbars=yes,resizable=yes,status=yes'
win = window.open("", "myWin", winprops)


form.target='myWin';
form.action='vista.php'
}

<form>

<input type="Submit" name="antes" value="Vista previa" onclick="cForm(this.form)" >&nbsp;
<input type="Submit" name="Submit" value="Enviar" onclick="this.form.target=''">&nbsp;
</form>