Use this option to specify a read-only row, column, or cell in the form. Use this option within a row or column definition or within a cell override definition. The read-only cell looks like all other cells but you cannot edit its contents. You can modify the style of a read-only row, column, or cell so that it looks different from editable rows, columns, and cells. See Style.
C4=S#Actual.Y#2009,ReadOnly