Just a quick note on the avoidance of the ** operator: I think as a general rule string manipulations are always far slower than math. I actually did try a variation on what you suggest myself (in a desperate quest for a better overall decode sub) and the benchmarks indicate the string route is very much slower (using 5 CPU sec run I went from 4800/sec to 4000/sec).

Update: tilly kindly offered this clarification: "Math will normally be faster if it already is a number. But converting strings to numbers to use a math operation, then converting back can go either way because of the conversion operation. (Usually better though.)"

Since this problem does boil down to getting strings, doing some math on them and spitting out strings, trying the all string manipulation approach could work if the math were just right.

--
I'd like to be able to assign to an luser