The attached document describes how you can add custom scripts on OLAP objects in TimeXtender.

There are four samples in the document that can be used for inspiration:

• Change the setting of the UnknownMember property on a dimension
• Insert description before the ID node of a cube
• Insert description after the ID node of a cube
• Add drillthrough actions to a cube

See this closely related post on how to modify a cube or dimension using XPATH.