Purchase order, voucher match, payment terms, commitment, ... how to deal with?

Hello JDEListers,

First of all I want to say that I'm quite a rookie in JDE, ... already feel sorry for the basic questions, ...

Here is my problem.
the company I'm working for is a engineering project company.

First let me drop that:
Project are created in JDE as business units that contain a nice detailed chart of accounts full of WIP accounts.

Project management is use to track the advancement of realization. our financial controller are also trying to calculate their cash flow.