I'll address the second question first.
On the sheet  change all of the cells to "unlocked".
Then select the cells you want to protect, and change
the property to "locked".
Now, when you protect  the sheet, be sure to remove the authorization
that says to allow users to select locked cells.
Now, record a macro in which you change  the protection  on the sheet.
The macro record function will not include the password.
What you have to do is something like:
MyPasswd = "testing"

Sheets("Sheet1").Protect _
DrawingObjects:=False, _
Contents:=True, _
Scenarios:=True, _
AllowFormattingCells:=True, _
Password:=MyPasswd
To unprotect, use:
Sheets("Sheet1").Unprotect Password:=MyPasswd
Of course you should password  protect your VBA modules to keep
users from being able to find your hard-coded password!