ConstTwo checkboxes over IStyle.getProtection() — Always unlocked and Show formulas — that act
on the selection the way a format control does: a mixed selection reads indeterminate, and a click
writes every selected cell. Like everything in the pane, a control commits when it is used.
Disabled while the sheet is locked, as Excel greys out its Protection tab: which cells are unlocked is exactly what protection keeps from changing. A pause lifts that like any other protection.
The Cells tab of Manage Protection: the protection format of the selected cells.