Problem:

First3 and Last3 are the defined Names for ranges A2:A4 and A5:A7 respectively.
We want to create a formula that will look up each of the values listed in column B for one of the defined Names listed in column C.

Solution:

Use the VLOOKUP and INDIRECT functions as shown in the following formula:
=VLOOKUP(B2,INDIRECT(C2),1,FALSE)