For title naming, I have a list of words that I employ. As I come up with new names, I want to make sure I'm not using words that have already been used. When I encountered terms that start with the letters AB (such as absolute, abolished, etc.) that I had never used before, my Excel formula appeared to be operating as intended. 
=IF(VLOOKUP(B48,Used!A:A,1)=B48,"USED","")
| New Word | 
Result | 
Formula Commentary | 
| Pretend | 
 | 
...VLOOKUP(B48,Used!A:A,1)=B48 correctly returns FALSE because it did not find the word | 
| Abundant | 
USED | 
...VLOOKUP(B48,Used!A:A,1)=B48 correctly returns TRUE because it did find the word | 
| Absolute | 
#N/A | 
...VLOOKUP(B48,Used!A:A,1)=B48 returns #N/A when it does not find any word that begins with AB | 
I've tried using the TEXT function in the formula to format B48, but no change. I've tried using Range_Lookup in the VLOOKUP syntax, but no change.
Any help would be appreciated.