form where a list of items populates from a spreadsheet

Yes, it's possible, but it requires quite a complex, custom-made script.

Also, if you want it to read from an external source then you need to

install a script on the local computer. A better alternative is to take the

source-data and attach it to the PDF. Then you can read and process it with

scripts located within the PDF file itself, and to update it you just

replace the attachment with the new data file.