Hi
First of all i don't see the necessity of haveing the relationship between country and shop
Country <-> Shop have the 1:n relationship. ( i think this relationship is not required)
since shop is related to city and city is related to country
so in-directly every shop is related to country.
i.e shop==>city==>country means shop ==> country
so please check your requirements do you really need this relationship? to me i doesn't make sense, since you can get the country of a shop in-directly as i told you above.
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Yes you can certinally achieve the effect through plugin. you can look at the following articles from msdn.
http://msdn.microsoft.com/en-us/library/dd393295.aspx
You can write a plug-in in any Microsoft .NET 2.0 CLR-compliant language such as Microsoft Visual C# and Microsoft Visual Basic. Each plug-in assembly must be signed, either by using the Signing tab of the project's properties sheet in Microsoft Visual Studio 2005 or the Strong Name tool, before they are deployed to the Microsoft Dynamics CRM server.
For more information about the Strong Name tool, run the sn.exe program, without any arguments, from a Microsoft Visual Studio 2005 Command Prompt.
See Also
Concepts
Reference
http://msdn.microsoft.com/en-us/library/bb955366.aspxbut as i said above please look at the relationship, i still feel shop ==> country is not required.
