Create a custom Shape map

Hi,

I have a file containing the mapping us postal codes --> internally defined territories --> internally defined Regions.
Our data is provided on the territory level and I'd like to show the data on region level with the possibility to drill down on territory level. Thus I need a shape map containing our definition of territories and regions. Is there a smart way how to create this type of map based on the data I have, where I can say, e.g. postal codes 90002 - 90312, 97005 - 97338 --> Territory WestCoast?

Thanks a lot,

Andre