function setupCategoryEditor(el, url) {
    var editor=new Ajax.InPlaceEditor(el, url);
    Object.extend(editor, {
        createEditField: function() {
            var text=this.getText();

            var field=document.createElement("select");
            field.name="value";

            this.editField=field;
            this.form.appendChild(this.editField);

            new Ajax.Request('/url/to/option/list', {
                onSuccess: function(req) {
                    // Get the text from an XML tag.
                    var getData=function(el, which) {
                        stuff=el.getElementsByTagName(which);
                        return stuff[0].firstChild.nodeValue;
                    };
                    var cats=req.responseXML.getElementsByTagName("cat");
                    $A(cats).each( function(cat, idx) {
                        var op=document.createElement("option");
                        op.value=getData(cat, "value");
                        op.text=getData(cat, "key");
                        if(window.ActiveXObject) {
                            field.options.add(op);
                        } else {
                            field.appendChild(op);
                        }

                        // Select the current item
                        if(op.text == text) {
                            field.selectedIndex=idx;
                        }
                    });
                }
                });
        }
    });
}