I assume that you have already looked at excel importer and that does not cater to your use case. Do you want to read all the possible values of the dropdown irrespective of the fact that the data may or may not have those? If yes, then you’d need to write a custom java action to read the excel file which is imported by the user or at the specific location.
Unfortunately, I don’t know if such a java action exists but looking at code of excel importer/exporter as reference and some basic java knowledge you could easily write one yourself!
Try use a excel importer and save values in domain model after you can call the table and show the rows