Sophia, I have done something similar using two copies of a layout, one for entering data and one that has all the data fields set to not allow data entry/modification. Then write a script that checks a lock field that if true sends the user to the locked layout, if false sends the user to the data entry layout. Set the script trigger on layout entry for both of those layouts and the user is automatically sent to the layout you want. You can use your confirmation button to set the value.
GoTo Layout ["entry"(table)]
Else GoTo Layout["entrylocked"(table)]
We use settings in Manage | Security... to keep users from modifying invoices on our system that have the text "printed" in a status field. This avoids the need for a second layout with script triggers and also permits users with full access privileges to modify them on the rare occasion when this is necessary.
See "Editing record access privileges" in FileMaker Help and check out this particular sub section: "Entering a formula for limiting access on a record-by-record basis" for a detailed description of how to set this up.
I haven't looked into that until now. A much more elegant way to do it. Will have to go back and clean out all those unnecessary layouts and scripts now.