It can get pretty tiresome referring to a range of cells by their actual cell address - eg: cells E17:F20.  It would be MUCH easier to give thse cells a name.  Something like:  "BonusTable".  You could also call January«s sales "SalesJan" or something. 

Then you could write a VLOOKUP formula something like this:

=VLOOKUP(SalesJan,BonusTable,2)

There are one or two things to remember before we start:  (1) Names can«t have spaces in them, and (2) Names act like absolute references.

Let«s look at how Excel«s own help file describes the process:

Forever after, this named cell (or range of cells) can be referred to in formulae simply by their name.

Watch out, however... you can«t fill-drag these formulae into adjacent cells, because "Named formulae" are like absolute references, and won«t automatically increment cell references as you drag.