You first need to think out the model or math you need to do what you ask...
Encode your script to match your model.
You might be able to buy a "Plug In" to do that already or use a web site like Bing maps to give you distances.
If you want to do it within your DB, you might think of using Latitudes and Longitudes of your disability organizations versus a key point's Lat/Long central to each postal code.
To search for records that fall in a range of values, you can set up criteria in a find request where you enter the smallest value, the ellipsis (...) and then the largest value. So if you want to find all records where the post code is from 2102 to 2122, you can enter this criteria:
while in find mode.
Such searches of your database can be scripted. See this thread for some examples of scripted finds: Scripted Find Examples
at its simplest your script would need to be something like:
Input 'known_postcode' (via Custom dialog)
Set Variable ($upper; known_postcode +10)
Set variable ($lower; known_postcode -10)
Enter Find Mode
Set field (postcode ; $lower & "..." & $upper)
Of course this does not allow for postcodes that cross states eg. enter 2996 and you may get Melbourne!
Thank you for taking the time to respond!
Given that I anticipate including potentially hundreds of disability organisations, the coding given by symbister is the best option, even though the addition of +10 and -10 could lead to the finding of unwanted locations. This was something i did not anticipate so thank you symbister for raising it! Hopefully, the addition of if..then trapping statements may be a workaround! I will need to check the Australian postcode book to find the range of postcodes used by each state then ensure that entered postcodes that are not true postcodes are eliminated and the user asked to re-enter the postcode.
Phil, what you have suggested will need to be done by the script. I need to keep it as simple as possible - the script will need to work off the postcode entered by the user. I will look at the link you mentioned!
Jim, I would not know how to do what you have suggested in using lat and long but thank you for taking the time to respond.
Yes this would be done in a script. If you check the link provided, it is a long list of scripted find examples.