Button to Attach document, lock attached document, add more later

I'm working in Adobe LiveCycle ES3.

I have a form where a button prompts a user to attach a document to the pdf file.  The PDF file is then electronically signed.  When the PDF file is signed, the information above the signature is locked.  The PDF file then goes to another user who need to fill in more information and attach another file, then sign and lock the next section of the PDF file.

Problem is I'm unable to attach any more documents once the first signature is placed and the initial attached document is locked.

Is there way around this? Is there a way to add additional documents to a PDF file after security locks the ability to access first attached document?

Thank you.