Dynamic Named Ranges
The more you work on Excel, the more indispensable Dynamic Ranges become. From simple data validation to conditional formatting and vlookups, dynamic ranges become the core referential element in Excel. The first page I ever read on the subject : Dynamic Pages on Ozgrid.com :
Possibly one of Excels most underutilised aspects is its ability to create dynamic named ranges that will expand and contract according to the data in them.
If you haven’t worked on them, now is the best time to start reading up.