iExpense - Could not get handle to the Attachments VO

On iExpense Final Review Page "FinalReviewPG" Submitt button, We have a requirement to throw the exception to user if he/she does not attach the Receipts Attachments with some specific Attachment Categories. In order to acheive this I need to get Handle to the Attachments VO but I could not as It throws the Java Exception error upon getting handle to the Attachments VO even though i added few ataXXhments and they showup on screen. Below is the portion of the problematic code and after that the full code. Thanks for your help.

//below is the problmeatic code

    OAApplicationModule RootAM = oapagecontext.getRootApplicationModule();