Now, there is an TabControl in my Application and sevel contorls in the TabControl(for example: TextBox & CheckBox, TextBox.text="aaa", CheckBox.Checked=true). I added an Button(Button.Enable=false) to the Application to check if the controls` content is changed. if TextBox.text="aaa" changed to "bbb"(or CheckBox.Checked=true changed to false), then i got the event to set "Button.Enable=true", if TextBox.text="bbb" changed back to "aaa", then i got the event to set back to "Button.Enable=false"