Hi Mike, 
   I have had the same problem with mice in a row home in Baltimore.  You 
have to find exactly how the mice are entering your home and put up some sort 
of physical barrier.  Usually they travel from house to house and no matter 
how much you do with traps and D-Con, they keep coming in.  In my case, they 
liked to come in by way of the cool air return, and around the gas line under 
the kitchen stove.  Because the basement had a ceiling, it was easy for them 
and hard for me to find the areas of entry.  I used a caulking compound for 
cement repairs to fill all the holes.  However, they still tried to gain 
entry through a 2nd floor bathroom ceiling.  If your neighbors are 
cooperative and make the same kind of effort, you'll be successful.  Hope 
this helps.
   Take care, Joe
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