Disable (or set to read only) some rows under spezial circumstances.

Add a custom method to you form called DisableGridRows() and put this code in it:

IF INLIST(Thisform.MyGrid.RowColChange,0,2) ;
     AND NOT ".INIT" $ PROGRAM(PROGRAM(-1)-1) ;
     AND NOT ".MOUSEDOWN" $ PROGRAM(PROGRAM(-1)-1)

   ***  row hasn't changed and this method hasn't been called from THIS.Init()
   *** and this method hasn't been called from THIS.MouseDown()
  RETURN
ENDIF

Thisform.MyGrid.AllowCellSelection = SomeCondition
IF NOT SomeCondition
  Thisform.MyGrid.SetAll("ReadOnly",.f.)
ENDIF

Now, add this line of code to the grid's MouseDown(), Init() and AfterRowColChange():

Thisform.DisableGridRows()