Caesar Cipher MOD VLOOKUP Function Help

I've done caesar ciphers in excel before, but am getting stuck on this one. I'm supposed to create every possible iteration of the ciphertext in F9-F14 through each of its translation factors. I filled out the expected output in G9-I14. I assume I'm suppose to use VLOOKUP on the ciphertext in the F column, look it up in the B column, find its number equivalent in the C column, add it by each translation factor (0 for column G, 1 for column H, etc) MOD 26, find that number in the A column, and find its letter equivalent in the B column, and fill in the cell with that letter.
For example, for the ciphertext in F9, I would look up B in Column B and find its respective number equivalent in Column C, which is 1. I would then take that 1 and add it by the first translation factor, 0 in G5, MOD 26, which is 1. I would then look up 1 in Column A and find its respective letter in Column B, which is B. I would then fill in G9 with B.
For the same ciphertext in F9, but instead for the next translation factor, I would again look up B in Column B and find its respective number equivalent in Column C, which is 1. I would then take that 1 and add it by the second translation factor, 1 in H5, MOD 26, which is 2. I would then look up 2 in Column A and find its respective letter in Column B, which is C. I would then fill in H9 with 10.
I understand the concept, but don't know how I'd implement this into a formula. I really just need one example shown out for me, and I can probably figure out the rest. Thanks in advance!

=char(1/iferror(1/mod(code($f9)+columns($f$1:f$1)-64,26),1/26)+64)

How exactly does this formula work? I'm trying to understand it so I can see where I can modify it to get my other desired outputs.

Originally Posted by tim201110

columns($f$1:f$1)

Why is this set to f1:f1? The f1 cell in the spreadsheet is blank.

The formula you provided gets the answer for the translation factor of 1, and I can modify that for each of the other ciphertext values in the F column, but how would it be modified to the other translation factors, such as 0, 2, etc.?

I figured out how to modify the formula to get my other desired outputs, thank you!