How to make a worksheet non editable ...even file extension change
 

I can make a worksheet non editable by using the worksheet property
objExcelSheet.EnableSelection = XlEnableSelection.xlNoSelection

also i am using the Protect document option with password.
The xls file cannot be able to edit. The document protection is achieved good.

The only problem that i am facing is If the xls file is changed to another
excel file extension say .ods (Open Office Excel document) the protection is
breaked. The password is not retained. The user can just uncheck the Protect
document sheet and can able to edit the document.

How to overcome this issue..