Would this work for you? It combines the three fields, replaces space with 0 (though I note that this may be redundant now) and lowercase letters with a numerical equivalent. Note it will leave all other characters (such as numerics, uppercase, symbols, letters with accents, etc.) unchanged.
var text combined = [text1] & [text2] & [text3];
var text space = SearchAndReplace($combined, " ", "0");
var text a = SearchAndReplace($space, "a", "1");
var text b = SearchAndReplace($a, "b", "2");
var text c = SearchAndReplace($b, "c", "3");
var text d = SearchAndReplace($c, "d", "4");
var text e = SearchAndReplace($d, "e", "5");
var text f = SearchAndReplace($e, "f", "6");
var text g = SearchAndReplace($f, "g", "7");
var text h = SearchAndReplace($g, "h", "8");
var text i = SearchAndReplace($h, "i", "9");
var text j = SearchAndReplace($i, "j", "10");
var text k = SearchAndReplace($j, "k", "11");
var text l = SearchAndReplace($k, "l", "12");
var text m = SearchAndReplace($l, "m", "13");
var text n = SearchAndReplace($m, "n", "14");
var text o = SearchAndReplace($n, "o", "15");
var text p = SearchAndReplace($o, "p", "16");
var text q = SearchAndReplace($p, "q", "17");
var text r = SearchAndReplace($q, "r", "18");
var text s = SearchAndReplace($r, "s", "19");
var text t = SearchAndReplace($s, "t", "20");
var text u = SearchAndReplace($t, "u", "21");
var text v = SearchAndReplace($u, "v", "22");
var text w = SearchAndReplace($v, "w", "23");
var text x = SearchAndReplace($w, "x", "24");
var text y = SearchAndReplace($x, "y", "25");
var text z = SearchAndReplace($y, "z", "26");
$z
