Beginner stuff - Adding look-up box to spreadsheet

New to this type of programming. Have snooped around the message board to see
if another question would help me, but it seems I'm lacking the very basics.

I would like to add a box to my spreadsheet that when a user enter a value,
the corresponding value from another column displays in another box.
So if I have:
Data 1 Data 2
1 a
2 b
3 c

the user would enter 2 in this new "entry box" and the "answer box" would
display b.

Thank you in advance.


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Thanks!!
Don