If you want to lock a variable to prevent it from being changed, use the Lock Symbols() function. (Lock Globals() is an alias.)
Lock Symbols( name1, name2, ... );
To release the lock and enable the global to be changed, use the Unlock Symbols() function. (Unlock Globals() is an alias.)
Unlock Symbols( name1, name2, ... );
The primary use of these two commands is to prevent inadvertent changes to variables. For example, locking a variable prevents Clear Symbols() from clearing a variable that is being used by another script.