I need to add the lookup value in PWA (Project online) Lookup table fields. Ex: when project is create in the project online that project name get added in the lookup table. Please help

I need to add the lookup value in PWA (Project online) Lookup table fields. Ex: when project is create in the project online that project name get added in the lookup table. Please help
I could use a bit more clarity on this. When you create a new project in Project Online, you have an Enterprise Custom Field value from PWA you want to read and add it to a lookup table where?? Back inside Project Online??
OR: When you create a new project in Project Online you want to add the project Name into an Enterprise Custom Field in PWA called some name like "List_of_Projects?"