data compile

hello all

I have a problem trying to figure out how to compile some data. I have two columns. One of zip codes and one of cities. What i need to do is remove the duplicate zip codes and list one cell for the zip code and one cell for the cities in that zip code and remove the
duplicates for the cities. The cities duplicates need to be removed once it is found
by zip code as different zips will have duplicate city names

eg

A         B
19503   Oakford
59711   Anaconda
59710   Alder
59711   Anaconda
59711   Fairmont
59711   Opportunity
58554   Saint Anthony
62673   Oakford
58554   Fort Rice
58554   Fort Rice
etc..

result I need
C         D
19503   Oakford
59711   Anaconda,Fairmont,Opportunity
59710   Alder
58554   Fort Rice,Saint Anthony
62673   Oakford
etc...

Any help with this would be appreciated. If the cities could be listed alpabetically that would be an added bonus but no worries.

Thanks
OMK