# OnSourceDestChange

The **OnSourceDestChange** event can be implemented by a [script add-in](../../../scripting/script_add-ins) to receive notification whenever a tab's source/destination state changes.

| **Method Name:**   | OnSourceDestChange                                                                                                                                                                                                                  |
| ------------------ | ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| **Argument Type:** | [**SourceDestData**](../scripting_objects/sourcedestdata)                                                                                                                                                                           |
| **Return Type:**   | _none_                                                                                                                                                                                                                              |
| **Description:**   | The **SourceDestData.tab** property identifies the tab, and the **source** and **dest** properties identify the new state (if both are **False** it means the tab is "off" - this can only happen in a single file-display Lister). |
