FileMaker Portals can't sort dynamically. You have two options to get the effect you describe:
Create a series of portals each specifying a different sort option and place them in different tabs of a tab control or in completely different layouts. You "sort" your portal differently by selecting a different tab or layout.
Create a calculation field or two that returns values from different fields based on the value specified in a global field or variable. You then specify this field or fields in your portals specified sort order. Now you can manipulate the order of the rows in the portal by changing the value of the global variable or field.
Many thanks Phil, it's good to know it wasn't inability on this occasion that was preventing me progressing and you've saved me a good deal of time keep trying.
I think I'll go for a dual layout approach and abort the notion of sorting each portal on the layout independently for the moment (too many permutations - too many layouts)
Sorting by name as I described before looks quite daunting by calculation at the present time, I'm looking to achieve this with an extensive value list that contains all likely possibilities, a bit of work, but it seems more straight forward, does this seem like a reasonable approach to you or is there a better way.
That value list approach seems pretty problematic. It could work, but it will be a lot of work to set up and it would be easy to get a value wrong in the list or leave one out.
I assume we are talking about the field that stores this data: z0/01/s, z0/01/s.1
I'd try to split those values into separate fields and then sort on the separate fields instead of this string.
I'll give that a go then, the name field is already calculated from a subset of other fields comprising the various parts of the name as a whole, so I likely don't have a lot of work in that case. Many Thanks for your help.
Actually I think i need a combination of both approaches, sort by subset fields and simpler much shorter value lists (I need to order things in an order that only make sense from my own perspective, ie... s, se, e, ne, n, nw, w, sw which follows no logical alphabetical or numerical order)