You define the nummerrange in 36.2.21 nrsqmt.p.
You have to create the include yourself. But I have embedded them in a procedure lib that I call.
I use this piece of coding:
Define your variables:
l_seqid as Character /* the name of the sequence */
If necesary you have to check the availability of the number with the related table.
With this routine the user and sequence are stored in the related sequence history.