Adding fields to Travel Services in Travel Request

Hi guys,

In our system, Travel Planning is disabled, because we don't want online booking. Travel services button is active in Travel Request, because we do want some basic information for each service.

I would like to know what's the best approach to store data of custom fields for each travel service.

Right now, I know how to add fields in the main view, using PTK99 structure, user exit, and enhancing the WDA application thanks to Lukas Weigelt.

Any help would be appreciated.

Thanks,

Raúl