No need for a program, although I'm sure it could be done if it's a must. Not my area of expertise.
Without a program and using your example, make sure layer 256 is visible and selectable. Format -> Move to Layer. On the Class Select dialog box that appears, make sure you have all options expanded and in the lower third of the dialog you'll see your filter options - pick the Layer filter, select layer 256, then OK (this sets up the selection to only pick objects on layer 256), then up at the top of the Class Selection dialog, pick Select All. This will bring up another dialog from which you pick the destination layer - make your pick and OK/Apply. Done.
You also can preselect objects then invoke the commands, if you prefer that route. The NX Help docs should assist in helping you understand that a little better. Note that you can filter by object types, colors, layers, attributes and select/deselect all from the Class Selection or Preselection filters.
Tim Flater
NX Designer
NX 9.0.3.4 Win7 Pro x64 SP1
Intel Xeon 2.53 GHz 6GB RAM
NVIDIA Quadro 4000 2GB