DI-API, SAPB1 V10 linking a document ( Journal) to a specific project stage

Hi,

I want to know if it is possible to automate the process of attaching a journal that would have been posted to a financial project, to a specific stage in project management, and set the "Categorise as" Invoice (AP), and also set the "operation" to Add

I can get the Journal in via DI-API, but the rest is a manual process in the GUI, and prone to error, so would like to automate this.

If any guidance as to which DI-API Objects etc could achieve this would be most appreciated

Thanks
Chris