By workflow module this is what I mean, given a document, there will be four signatories. Once the first signatory hasn't approved the document yet, it can't be accessed by the other three. Then the moment he or she approves the document, the second signatory then can access the document while the first signatory losses its access to it. This goes on until it reaches the final signatory and only then will the document be approved.

Is there an exsiting module for this? I have searched SugarForge but couldn't find any. Would it be too ambitious to construct a module like this form scratch? Thanks for all your inputs.