Emulating a multi user accessed spreadsheet on Appian using editbale inline grid. (Question) (Best Practice)

Someone is asking me to create the functionality of a shared excel spreadsheet on Appian. They want multiple business users to be able to log in and access this spreadsheet and make modifications to it so that others can see it. (Kinda like Google Docs)

My question is, what would be the best way to do this?

I created a CDT with all the columns that they want on the spreadsheet.

I created an interface with an editable inline grid where you can add and remove rows.

Now how can I make it so everytime they add/delete or modify data that it reflects that in the database so that next time they come back, it reflects what they did. 

Any advice is appreciated.

Thanks,

Note:I tried to create a process model that passes in a CDT multiple array and the interface can add or delete or modify to that CDT multiple array and then write back to the database, but it appears that when adding a new row in the editable inline grid, it doesn't generate an id field (rpimary key) which I think may be causing a problem. It works for modifying data though, and I haven't tried deleting yet.

Any thoughts?