MSCRM 2011 depended optionset

There is no need to create something that is already there.

There is a very good (generic) solution for depended optionset (picklist) in the SDK.

http://msdn.microsoft.com/en-us/library/gg594433.aspx

The problem is it's technical solution, That's mean you'll probably need developer next to you when you do it the first time. 

Maybe I'll create GUI for it one day. :)