You can apply security to the workbook by the concept of protection available in the Review Tab of ribbon.
You may want to protect a worksheet for a variety of reasons. One reason is to prevent yourself or others from accidentally deleting formulas or other critical data. A common scenario is to protect a worksheet so that the data can be changed, but the formulas can’t be changed. To protect a worksheet, choose Review >> (Changes group) Protect Sheet. Excel displays the Protect Sheet dialog box. Note that providing a password is optional. If you enter a password, that password will be required to unprotect the worksheet. You can select various options in which the sheet should be protected. Suppose we checked Format Cells option then Excel will not allow to format cells.
When somebody tries format the cells he or she will get the error as below.
Excel provides three ways to protect workbook.
When a workbook’s structure and windows is protected, the user may not Add a sheet, Delete a sheet, Hide a sheet, unhide a sheet, etc and may not allowed to change size or position of workbook’s windows respectively.
Excel lets you save a workbook with a password. After doing so, whoever tries to open the workbook must enter the password.