P/Invoking a custom DLL not in the system path

[lonewolf32]

How do I P/Invoke a DLL that I wrote in C, that is not in the path? I need to do the following steps in C#:
- Query the registry to find the location of unmanaged DLL
- Somehow communicate the location of the DLL to P/Invoke
- Then utilize the member functions of the unmanaged DLL

If I put my unmanaged DLL in system32, P/Invoke finds it fine and I can utilize its functionality however this is not an option on the customer system. The unmanaged DLL gets installed to a Program Files directory that the customer can change, and its not the same directory where my C# assembly is located.

Thanks!