Jerry,
I think zip code assignments are more a matter of number of people than physical area. So I imagine you need to use some kind of mapping software to accomplish what you're looking for.
The folks at
www.weber.com do this and perhaps you contact someone there who could give you some pointers on how they do it.
HTH,
>Is there a way to determine distance from a zip code?
>
>For example, we would like to point our customers to a dealer closest to them. We would like to have the customer enter in their zipcode and then we would like to display a list of dealers in their area, within 50 miles.
>
>Is there a calculation to use, such as: the first 3 digits of the zipcode will be a 50 mile radius and the first 4 digits will be a 25 mile radius and so on?
>
>Thanks,
>
>Jerry
Jim