creating a new data type

hello,
i am using VS2010 and the included SQL Server Express Edition 2008 SP3 (10.00.5500.0 x64).  i would like to add a new data type, but the when i right click the "Types" folder, the option to do so is not listed.  i only see "Refresh" and "Properties" in the option list.
is there something i am missing or is there some other way to create/edit the new type?
thanks!

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