As explained in Excel's documentation, you can customize the Excel UI by placing an .officeUI file in a specific location.

XLS Padlock allows you to specify your own Excel.officeUI for the secure application. It will automatically replace the user's default UI (if available).

You have just to enter the full path to the Excel.officeUI file you want to use. XLS Padlock will compile it into the final EXE, so no need to deploy the Excel.officeUI file separately.

For further information about creating custom UI XML files, please refer to the documentation of Excel: