Okay, I have 2 columns, Topic & Subtopic. The topic column cells are data
validated with a drop-down menu to a range of 30 values on another sheet
labelled "Topic". In the next column, Subtopic, I want the cells to also be
data validated with a drop-down menu, but dependent on the value in the Topic
column. So that each Topic has a unique set of Subtopics to choose from.

I figured out how to make a List Data Validation that has a nested if/then
function for the Source, which works, but you can only nest up to 7 if/then
functions, which limits me to 7 topics, when in fact there is about 30.

Any ideas? Thanks