Maskprocessor word at position??

Hi is there a way get a mask word by position or range of index.

?u

returns A-Z so instead of

?u -s M

I want to write

?u -s 13

eg

mask[0-10000000]
mask[10000001-20000000]

etc

as far as I can see it is not possible to split a mask via words and still generate all posibilities. or is there?

thank you!