You must have generally "Quads" faces of the object for make SUbdivisions
or no more 5 polygons !


So make first this sort of face subDivision




Or more generally you can use sSplit, sBridge, sScale By Max Smirnov
http://moi3d.com/forum/index.php?webtag=MOI&msg=6674.254

(in this object Top / Bottom faces will not subdivided - too much polygons)

Here use sSplit (don't select object but FACES-edge !!! )



Use only SBridge for create the "Bridge(s)" face to face (make them manually will not works for the SubDivision)

and then use SubDivision :)