Excel formula to power query M code

This is fairly complex but it does match the Excel result (when all the letters are upper case). Add a custom column and put the code below in the pop-up box, replacing TextColumn with the name of your text input column.

let 
input = Text.Upper([TextColumn]),
letters = {"A".."Z"},
concatvalues = {null, "A".."Z", "0".."5"},
splitinput = List.Split(Text.ToList(input), 5),
lettercheck = List.Transform(splitinput, (x)=> List.Transform(x, (y)=> Number.From(List.Contains(letters, y) ))),
multipliers = {1,2,4,8,16},
listsums = List.Transform(lettercheck, (a)=> List.Sum(List.Transform({0..4}, (b)=> a{b}*multipliers{b}))),
listvalues = List.Transform(listsums, each concatvalues{_+1}),
result = input & Text.Combine(listvalues, "")
in 
result

Pat