Hi Amy. Amy that attended UC2008 Amy?
Are you saying that you have more vendors listed in the current table window than are listed in the external lookup file (xls or mdb or what have you)?
The lookup will generate null values for key combinations that it can't match in the lookup file.
You'll need to do whatever it takes to generate a full vendor list in your external lookup file in order to be able to import data based on a common key via an external lookup.
[URL="http://********************/xlreport/use-monarch-to-build-a-report-with-both-details-and-a-summary"]Nigel outlined a good approach that you might be able to use[/URL] to populate your master list. Essentially it involves creating a new table (overwrite option) with a first project file. Then with a second model/project, you recreate the exact field names and sequence as appear in the first model/project, and append that data to the output of the first file export.
That will get you a good master list that you'll be able to use for your subsequent external lookups.