Determine control and parsing strategy for offset filter when choosing zones to apply

[zspitz]

From this comment:

Each zone has a MinOffset and MaxOffset property. We could also allow specifying an offset, and the list/treeview could be filtered based on whether the filter offset falls between the min and max offsets.

But we really need to figure out what kind of control could be used to select an offset. I can't think of a simple and easily understood way to do to this.