IF_WD_CUSTOM_STYLE_MANAGER is unknown

Hey,

I just found this tutorial which looks pretty like what I need. (Custom Styling For Webdynpro ABAP UI Elements)

I copied the code but it tells me that the field 'data' is unknown.

When I want to create the custom style manager like

DATA lo_custom_style_manager TYPE REF TO IF_WD_CUSTOM_STYLE_MANAGER.

from this source UIElement Properties - Web Dynpro ABAP - SAP Library ,it tells me that 'IF_WD_CUSTOM_STYLE_MANAGER' is unknown.

I saw a few post which solved their problem with the code from the scenario but I couldn't apply it for some reason.

Thanks for any hints!