\psset{unit=.5cm}
\begin{pspicture}(10,10)
  \psset{subgriddiv=0,linewidth=.8}
  \psgrid
  \psframe[dimen=inner](1,1)(4,4)
  \psframe[dimen=middle,linecolor=red](6,6)(9,9)
  \psframe[dimen=outer,linecolor=yellow](0,6)(4,9)
\end{pspicture}
