Dynamic Linked Validation Lists

I have a spreadsheet where I keep all records of all the rock climbing I have done.

I am after a way of choosing a climbing area either by data validation or combo box (already set up as a named range) and then the climb names available in another validation list shows only those from that particular climbing area.

From what I have seen from various web sites it seems the climbing area names need to be in a unique list (is this correct). My sheet looks like the following:

Column A | Column B (climbing area) | Column C (climb name)
Date | Mt Arapiles | Agent Orange
Date | Mt Arapiles | Auto Da Fe
Date | Morialta | Asgard
Date | Morialta | Al Sirrat
Date | Buckaringa Gorge | Agent Orange

The name in the climbing area column will be repeated often.

The climb name should be unique to each climbing area, but the climb name my be repeated in another climbing area.

The climbing areas are anamed range on a separate worksheet.
The details of the climbs has all the details of the climb i.e. the Climb Name; Climbing Area (VLookup); Grade ; Distance ; Single or Multi Pitch ; Lengths of each Pitch.

I already have a working example of the spreadsheet (220KB) but it currently works backwards i.e. I use validation to find the climb name and then this uses the INDEX function to return the climbing area.

I would like to be able to choose the climbing area and then the next available choices would be limited to that climbing area.