Project Standard Cost Descriptive flexfield cutomization

Summary: I have requirement to have Project Name field to be displayed in the AP invoice lines along with other POET information

Content (please ensure you mask any confidential information): The requirement is to have a separate filed as "Project Name" in the AP Invoice line along with the other POET information. This Project Name field should get auto populated based on the Project Number enter by the User while filling the POET information. How to achieve this.

I have tried editing the Project Standard Cost collection flexfiled however, I am getting stuck by some error. Would be really helpful if any one had such similar requirement and could let us know the exact steps to perform to achieve this.