Using macros on a protected workbook

And what exactly do you want to do (because you mark minimum millions of cells, and then you're trying to unhide minimum tens of thousands of rows) ?

    Cells.Select
    Selection.EntireRow.Hidden = False

Old excels = 16,777,216 cells = 65,536 rows x 256 columns
New excels = 17,179,869,184 cells = 1,048,576 rows x 16,384 columns