Keeping track on changed values

I have created a GUI where I have a table that contains subscriptions, and each row contains information about a subscription such as name, last edited and country. When a subscription is selected a form below the table shows more details for the selected subscription (master/detailt I believe this is called).
The user can now change the value in the form, for the selected subscription.
No my task is to make this as easy as possible to use for the user. He should be warned if he selects a new subscription without saving his changes first, but also I do not want to warn him if what he did was to change a few values and then changed them back again (yes users do that kind of thing instead of clicking “discard changes”).

Does vaadin have any features to help me in this? I am aware of the isModified() method, but the whole thing with warning the user I have not been able to find. Nor does the isModified() return false if the user changes a value back to what is was before editing.

Is this not a feature that could be so generic for vaadin to support it?