ASP.NET - Crear un Iframe de solo lectura

function OnIframeTestReady()
{
    //Override the onmousedown event
    crmForm.all.IFRAME_Pedido.contentWindow.document.onmousedown = function(){
                alert("La ventana es de solo lectura");
                return false;
    };
}
crmForm.all.IFRAME_Pedido.attachEvent( "onreadystatechange" , OnIframeTestReady );
crmForm.all.IFRAME_Pedido.src = "../isv/default.aspx?so=123456";