This example shows how you can implement an evaluation unlocking system. testKey is a variable associated with a text input box. ErrorText and EnableText are text object with suitable messages in them.
The EnableText object could have an On Show trigger with a Set Publication Evaluation action to clear the evaluation flag so the user is not prompted in the future.
if ( TestPublicationKey( testKey ) == true )
{
// The text object "EnableText" has an On Show trigger
// with an action to disable the evaluation in future
EnableText.Show()
}
else
{
ErrorText.Show()
}