The short answer is that you should re think your database.

From the question it is clear that the field is storing at least three separate entities:

Sector (3-13) - varchar

PropertyID (414) - int

Sub Property ID (/a) - varchar

To do the sorting that you want, you will need to split the value into three, sort by the middle and last columns and then recombine the values. Longer term it would probably be better to store these permanently rather than split and recombine each time.

If you can't change the existing columns, you could possibly add computed columns to the existing table, or create a lookup table with Create, Update and Delete triggers on the existing table. Failing that, a table function would do it, but performance may take a hit, depending on the size of the dataset being processed.