There are international forums. Would one of these help if you wrote in your native language or another?
yes I know Beverly, but none answer me again. At this time I found solution with my macchiavelli type formulas, waiting some other simple way.
I'm not sure how you'll be using this, but if all you're looking to do is figure out what a future month's adjusted number is based on a new starting month, a custom funtion with the following formula might help.
startmonth = StartMonth ;
diff = (12 - startmonth) + 1;
adjustedmonth = MonthN + diff
adjustedmonth >12 ; adjustedmonth - 12 ;
If you pass it two parameters - start month (as a number) and the month you're looking for (as a number), it will return the adjusted month.
So, to use your example of October, we're assuming that October is now month 1. The distance from 10 to 1 is 3. So then you add three to every month after that, allowing that numbers greater than 12 will flip back to 1. So, in this example, October is 1, November is 2, December is 3, January is 4...
There are many other ways to do this. This is just a simple way. Hope it helps.