Sorting ignores special characters.
You won't like the answer, but there are no custom sorts in WebI.
Change your values so that they are alphabetically in order
151+
101-150
051-100
001-050
This works. It doesn't look great, but it does the trick.
When you get custom sorts in XIR2, then you can make it work the way you want.
Steve Krandel
Symantec