Do I Disclose Prior Art for Double Invention?

Dear Rich: I have an invention.  It handles a specific problem.  While writing it up I discovered it handles another related but different problem for which there is prior art totally unrelated to the first item.  I know from Patent It Yourself that I can't do a double patent.  Both are valuable and I need to protect both.  Do I need to do the full prior art and so on for both?  It would be like writing up two patents in one.  Is there a way to do one then tag on the second so as to not increase my chances of rejection by going for two separate things? We spoke with Patent It Yourself author David Pressman who stated that it would be irresponsible for any patent attorney to give you advice without seeing the invention and the prior art so he urges you to seek professional advice in this situation.
That said dept. However Pressman notes one general principle that may apply is as follows: Suppose an invention is known for solving a problem, for example, a forked implement is known for cleaning window blinds. An inventor discovers that it can also solve another unrelated problem, such as facilitating seed planting. In this situation the inventor may be able to get a patent on a new use for the implement if it is truly novel and  unobvious over the known use. This is mentioned in the sixteenth edition of Patent It Yourself (page 103) and elsewhere. In any case PTO Rule 56 requires the inventor to disclose all information related to patentability.
Dont try this at home dept. Again Pressman stressed that this should not be construed as legal advice or applicable to your situation and you should see a licensed patent pro before deciding what to do.