Try this code.. you need to override WndProc in your own custom datagrid
control. Hope this helps.

 protected override void WndProc(ref Message m)
 {
  IDataObject clipData = Clipboard.GetDataObject();
  bool ctrlDown = false;
  bool shiftDown = false;
  bool handledMessage = false; // used to decide if call to base WndProc
needed.
  switch ( m.Msg )
  {
   case 0x0100 :
   {
    if((int)m.WParam == 0x0011)
    {
     ctrlDown = true;
     break;
    }
    if((int)m.WParam == 0x0010)
    {
     shiftDown = true;
     break;
    }
    if((ctrlDown == true) && ((int)m.WParam == 0x0056))
    {
     handledMessage = PerformPaste();
     break;
    }
    if((shiftDown == true) && ((int)m.WParam == 0x002D))
    {
     handledMessage = PerformPaste();
     break;
    }
   }
    break;
   case 0x0101 :
   {
    if((int)m.WParam == 0x0011)
    {
     ctrlDown = false;
     break;
    }
    if((int)m.WParam == 0x0010)
    {
     shiftDown = false;
     break;
    }
   }
    break;
   case 0x0302 :
   {
    handledMessage = PerformPaste();
   }
    break;
  }
  if(handledMessage == true)
  {
   m.Result = new IntPtr( 0 );
  }
  else
  {
   base.WndProc(ref m);
  }
 }

 private bool PerformPaste()
 {
  //custom past operation implementated by user
 }