I am creating a document with several long lists. I se theu lower case letter format and it works fine until I get past z. Then it goes into double letters, aa, bb, cc, etc. I'd like it to work like this instead:

x.
y.
z.
aa.
ab.
ac.
ad.
.
.
ba.
bb.
bc.

Is this possible? If so how would I do this? Thank you for your time.