inspector dynamic dropdown list

I have been searching the web but have not been able to find a solution to my problem as of yet. I am currently writing a program for the asset store which requires things to be added to a list dynamically from outside the script. What I am looking to have is a dropdown menu similar to the one in the mesh renderer called Materials, where the number of variables can be input and then in the drop down menu that many fields will be available. I realize that there are ways to do this with new pop up windows, but I would prefer to keep it all in the inspector if I can. Thanks in advance for the help.