Create a bindable boolean variable in the form page say [Bindable]private var formChanged:Boolean = false;
set this to true in the change events of any of the form input fields.
Buttons enabled state can be bound to this boolean property like this
<mx:Button id="btnCommit" enabled="{formChanged}"/>
<mx:Button id="btnUndo" enabled="{formChanged}"/>
<mx:Button id="btnDone" enabled="{!formChanged}"/>
After the data is committed to the database, set the formChanged to false