Row grouping increments

[jeffrey7]

I have a pivot table in which the first column looks like this:
1
2
3
4
5
...
50

If I group them in increments of 5, I get the following:
1-5
6-10
11-15
...
46-50

I would like to group like this:
1-5
2-6
3-7
4-8
5-9
6-10
...
46-50