Custom newfrom (upload a picture and fill in the picture url)

I have to customize an announcement list new and edit form.

In the form is there is a Picture Colum. But I don’t want the user to go first to a picture library, upload the picture, copy the picture url and fill in the url in the announcement list form.

In the Internet I found this helping jScript (http://spimagefieldupload.codeplex.com/).

//If the link is clicked, show the existing RteUploadDialog.aspx page as a popup
            var dialog ={
                url: SP.Utilities.Utility.getLayoutsPageUrl("RteUploadDialog.aspx")+"?LCID="+ SP.Res.lcid +"&Dialog=UploadImage&UseDivDialog=true&Source="+ encodeURIComponent(window.location),
                allowMaximize:true,
                showClose:true,
                width:500,
                height:160,
                dialogReturnValueCallback:function(success, html){
                    if(success){
                        //Gets the picture's url from the popup, shows it and hides the links
                        var $emptyPanel = jQuery("#"+ selectorId +"_EmptyPanel");
                        var $assetSelectedPanel = jQuery("#"+ selectorId +"_AssetSelectedPanel");
                        var $imageFieldDisplay = jQuery("#"+ selectorId +"_ImageFieldDisplay");
                        $imageFieldDisplay.html(html);
                        $emptyPanel.css("display","none");
                        $assetSelectedPanel.css("display","inline");
                    }
                }
            };
            thisDialog = SP.UI.ModalDialog.showModalDialog(dialog);

But how i can change the script (dialogReturnValueCallback: function) so that the picture url and the picture name is stored in jScript Variables in the form. So I can write I back in the form fileds.

Thanks for your help