From Xojo Documentation
Unlocks the keychain if the password is the empty string ("").
The system displays the standard Unlock dialog, and the passed keychain will appear as the selected item in that dialog's pop-up menu. NOTE: because of the way Apple has implemented this, if you pass an incorrect password once to a particular keychain, the system will require human interaction from then on that keychain until the system is rebooted.
If it fails, it generates a KeychainException.