You're on a virtual Mission Impossible. There is not way to keep a
determined person from eventually getting to anything in an Excel workbook.
As you've noted, tools for cracking workbook and worksheet passwords are
readily available and the level of protection is so weak that they all work
fast.
Here's the best I can offer (and is in addition to any password protection
you put on the worksheets and/or the workbook):
Step 1 - make the sheets as hidden as possible; preventing them from even
appearing in the Format | Sheet | Unhide list.
You need to get into the VB Editor to do this. Press [Alt]+[F11] to open
the VB Editor. If you do not see a small window labeled something like
"Project - VBAProject", press [Ctrl]+[R] or choose Project Explorer from the
View menu.
Next you need to be able to set the Visible property for the sheets you want
to hide well. You need to be able to see the Properties window for this - it
will be titled "Properties - ..." where ... is the object you have selected
in the Project window. Choose one of the sheets to be hidden in the Project
window. If you don't see the Properties window, press [F4] or choose
"Properties Window" from the View menu.
With the name of one of your sheets selected in the Project window, find the
Visible property in the Properties window and click on the setting which has
a drop down list, choose the "2 = xlSheetVeryHidden" option. Now that sheet
will not even appear in the list of sheets available to be unhidden in the
main Excel window. Repeat this for the other two worksheets.
While still in the VB Editor, choose Tools | VBAProject Properties. Select
the [Protection] tab and check the box next to the "Lock project for viewing"
setting and then enter/re-enter a password for the project. Be sure this is
either a password you can easily remember, or WRITE IT DOWN and put it
someplace safe. Password protection on the project is much stronger than on
worksheets/books, but is still susceptible to being cracked (I've got a tool
here that does it very well and quickly, myself).
Save and close the workbook. Open it back up and try to view things: press
[Alt]+[F11] to open the VB Editor. It will open, but you shouldn't see
anything of any use. If you try to expand any of the lists in the Project
window, it should request the password from you. That should stop all but
the most determined from being able to even see the sheet names of the well
hidden sheets.
Hope this helps you some.
I need to protect 3 sheets in a workbook from being unhidden. I know
Excel has the password protection at the time you open and the
worksheet protection. I also know there is a large number of products
that can break these.