If, at any time, you want to block a user from viewing or editing your spreadsheet, here's what to do:
1.
Click the Show Sharing Options link. The list of viewers now appears at the bottom of the sharing pane, as shown in Figure 44.
2.
Click the Remove link next to the person for whom you want to rescind viewing/editing privileges.
That's it; the person you selected will no longer have access to this spreadsheet.