Hi,
I just downloaded and tried your file. It just works, doesn't it? 
A Worksheet_Change macro runs automatically when you make a change on your sheet (in your case, sheet 1).
When I type a password in cell D8, it changes to ***** right away - if I type the right password, sheet tabs 2-5 are visible and the buttons work, if I type the wrong password, they are not.
The button 'run' isn't needed anymore and doesn't do anything indeed.
A list of passwords on the sheet is also not needed any more. Even the list with user names isn't, unless you want to keep working with a dropdown list.
What the sheet doesn't do is give a message when a wrong username or password is entered. If you want to include this, change the code as follows :
Put it in between here :
If the sheet for you doesn't automatically do the things I said above (and you're sure you enabled macros), it might be that your excel bugged at event checking some time and it's halted now.
Either close excel entirely and re-start it and open the file, or go to the VB editor (Control + F11), and press Control + G to open the "Direct" window.
There type :
Application.EnableEvents = True
and press enter.
Now go back to the sheet, it should work fine.
Let me know if you have any other questions.
Oh and please click the * below if this helps 
ps - one last thing ; if you are going to give this sheet to users, you'd do well to protect the VB code with a password ; otherwise any user can just check the VBA code to see usernames and passwords.
Do this by in the VB editor go to the menu "Extras" on the top, select "VB properties" and go to tab "Protection" - there tick the box that says "lock the project from viewing" and enter a password below it.
Also, if you want to protect the sheet from users checking other people's data, change this part of code :
From :
To:
What's the difference? A sheet that's merely hidden (.visible = false) can be made unhidden by the users, by clicking on a visible tab sheet and say "unhide", where they can see and select hidden sheets to unhide.
A sheet thats "visible = xlveryhidden" is invisible from within excel itself, can't be unhidden by the users and only be unhidden from a macro.
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