Google Docs provides users with option for restricting the access to the spreadsheet. Users can protect a spreadsheet the following ways
Click on the Sheet name available at the bottom of the spreadsheet. Select Protect sheet from the list of available menus.
This would display the following Protect sheet dialog box.
In the above dialog box you can assign the users who can edit this sheet. For example, if you want to be the only editor then select Only me radio option and click on the Done button.
Another way to bring the Protect sheet dialog box is using the Tools menu. Click on the Tools menu and select Protect sheet from the menu list.
A protect sheet will have a lock symbol as shown below.