Is it feasible or possible to add a custom form portlet on a dashboard that allows a user to select a zip code that calculates the distance between the selected zip code and all of the other zip codes in an adjacent search?

I added a custom record that contains all US zip codes and their longitudes and latitudes.  I have a search with a numeric formula that can measure the distance between two latitude longitude points in miles (Great Circle Distance Formula).  My issue is that some of my users are not savvy with changing the SQL code in these search formulas and they need an easier way to enter the starting point.