Es mas o menos esto .
Código Code:
Ver original<script>
function WinOpen(pag){
var url = pag + "/mipanel";
window.open(url,"url","width=700,heigth=400");
}
</script>
<form name="form">
<input type="text" name="url" value="http://">
<input type="button" border="Ir" onClick="WinOpen(document.form.url.value)">
</form>