Individual orders may be "locked" so that they cannot be changed. This is accomplished with a lock button just to the left of "Order Details". The button also indicates whether or not the order you are looking at is locked.
The ability to lock and unlock orders is determined by one's "user level", which can be set on the configuration form.
The levels are as follows:
1) read and make reports only
2) create orders, cannot lock or unlock
3) full control
By default, new users are set at level three. After the program is purchased, the user level cannot be changed without the program registration key as a password.