Thank you Montag DP !!
It has taken many and many try and re-try.. i haven't found a good manual on macro usage on Rhino, but finally here it is the alias that does what i've done manually :
! _DupFaceBorder _Pause _Offset _Pause _Pause _SelLast _FilletCorners _Pause _Pause _MakeHole _Pause _Pause _Enter
It gives the possibility to choose the inside offset distance, the fillet radius and the object that you want to empty
This software is incredible !! i've tried to learn how to use it for years without success, then Harpye has shown me the light and a whole new world was opened before me :-P