From Xojo Documentation

Property (As Boolean )

aAddressBook.HasUnsavedChanges = newBooleanValue
BooleanValue = aAddressBook.HasUnsavedChanges

Supported for all project types and targets.

If True, a Save is needed. Call the Save method to save the changes.

Sample Code

Dim book As New AddressBook
book = System.AddressBook

If book.HasUnsavedChanges Then
If book.Save Then
MsgBox("The changes were successful!")
End If
MsgBox("There were no unsaved changes!")
End If