Inline Synchronous ScriptCallback

Currently I am using Asynchronous ScriptCallbacks in my web app to get data from the server without postbacks.  My code currently looks something like this:

ASPX CODE:
function ServerLookup(id)
{
DoLookup(id,0);
}

function OnResultReturned(arg, ctx)
{
//process arg
}
CS SERVER CODE:

string js = Page.ClientScript.GetCallbackEventReference(this, "arg", "OnResultReturned", "ctx", true);
Page.ClientScript.RegisterClientScriptBlock(this.GetType(), "0", "function DoLookup(arg, ctx) {" + js + "}", true);
//////
This cu ...