I was making a puzzle which started with a piece of text, used the Caesar shift (rot-N) on each letter, then converted the Ns to letters (1=A, 26=Z) to spell out the co-ordinates.
If my message was HELLO and my key text CACHE, then the cipher text would be UVQVP.
As I was doing it I realised the easiest way to set it would be with a grid of letters similar to one used for the Vigenere cipher.
Rcqkfxd, Zunhiw, Xaqimzthlt, dvvj nk qwpm olie;
O ofyz nf fpxq Kvzsar, not to praise him;
The evil that men do lives after them,
The good iv jmz tzokumqj xows pcxqm wvhvw;
Ny wvf oa sg rzmz Igwavm.
FTF Congratulation to Tobias & Petronella