load and unload dll(assembly) at runtime in windows application

Question

Hi friends,
i have one query:
Initially I am checking the version number of the dll from my remote location,that version number is greater than the existing dll version number in my windows  application.then I need to delete the existing dll from my application at runtime and load the new dll from the remote location at run time only.

if any one can help or provide a link with  code i will be thankful to u.
or
can explain with example
advanced thanks