The CTF we were playing this evening had a gronsfeld cipher, so here is my first stab at a function that would solve it. Due to the way I am rolling through the alphabet all characters must be uppercase (and specials removed or stripped in the func, i opted for removing them manually for example purposes), any improvements are welcome.
local $aTestKey[8] = [0,7,2,7,1,9,7,8]
$aTestStrCreate = stringsplit(stringupper("ICECTFIDONTTHINKGRONSFELDLIKESMONDAYS") , "" , 2)