Filling Multiple Columns In A Table From One Combobox?

I know how to have multiple columns fill a lookup in a combobox both from a table and a query. But I need to have the other fields that aren't saved by the combobox saved in the neighboring columns. So, my primary table is a master list of chemicals to be analyzed along with their respective registry numbers. I know what most of the programmers say about repetitive data being bad form etc. These names and registry numbers will NEVER change, so I'm not worried about a change causing problems later. I'm trying to build a separate tables that will have specific chemicals and the methods that they are analyzed under that effectively copy from the master list, but add their own quality control criteria. Further more, not all of my clients need all of the chemicals that are available for every method. It should be noted that not all chemicals are analyzed by the same methods and that some methods will have some of the same chemicals as others. I need the registry numbers because this is what the analysis software uses to uniquely identify each chemical and I need the name because names are easier for me. Long story short, I need both of these pieces together. It was suggested to have a macro copy the remaining columns from the dropbox in the table to the other columns in my table, but I'm not sure how to do this (I'm still very new to Access and my VB is very rusty). I understand how to do this for a form, but when client reporting lists become involved later on, this will make my database very bloated to have a form to populate each respective table.