The dynamic geocoding can be accomplished by importing your table of addresses to your map, right click the table in the TOC and select geocode addresses. Choose an appropriate address locator and click ok. In the next window, in the Output section, you will have the option to create a dynamic feature class. If it is greyed out, just make sure the output location for the geocoding results is the same location as where you are keeping your table of addresses. It then appears to set up a relationship class between the table and the geocoding results, making it dynamic. If you make the locations the same and it still won't give you the option to create a dynamic feature class, then it may be a liscensing issue.
I believe edits must be made to the table in ArcMap in order for it to change the geocoded points. I've never tried this with an excel spreadsheet.