dynamic setting parameter values of MBO in custom.js

Hi all,        

       i am developing WF, my requirement is  sending image to SAP.

in sup 2.2  I did the following,

1. created the MBO ( MBO is BAPI with logic of BASE64 to image )

2.Added the create operation to MBO. ( the data type of image parameter is BIGBINARY )

3.in start screen, i  added the menu item ( 'get_picture' as type online request and invoke operation is create )

4. I wrote the following code in custom.js

function customBeforeSubmit(screenKey, actionName, workflowMessageToSend) {

    if (screenKey == "Start" && (actionName == "Get_Picture")) {

        var form = document.forms[screenKey + "Form"];

        if (form) {

                  var popover = new CameraPopoverOptions(300,300,100,100,Camera.PopoverArrowDirection.ARROW_ANY);

                   var options = { quality: 40, destinationType: Camera.DestinationType.DATA_URL,sourceType: Camera.PictureSource.SAVEDPHOTOALBUM, popoverOptions : popover };

                   navigator.camera.getPicture(onSuccess, onFail, options);

                   function onSuccess(imageData) {

                             MBO cust = new MBO();  // MBO is my MBO name

                       cust.setIM_IMAGE ( imageData ); //im_image is parameter of MBO

                      cust.setOBJECT_ID( "Sybase" );

                      cust.create();

                  /*    var image = document.getElementById('myImage');

                      image.src = "data:image/jpeg;base64," + imageData; */

                  }

                  function onFail(message) {

                      alert('Failed because: ' + message);

                  }

            }

        }

5.Following warning showing.

Operation argument 'MBO->create()->IM_IMAGE' has large object type 'BIGBINARY', but is not mapped to an attribute of the same type. Thus, it will not leverage the streaming I/O mechanism.

It is not working. anything wrong i did?

Thanks

Suresh