C# - Registering dependency dlls necessary for COM Visible Class?

C# - Registering dependency dlls necessary for COM Visible Class?

I have a C# library that was developed in-house to provide an interface to
our legacy software. Over the time requirements grew and now here I am to
add COM visibility to this interface library so that it can be accessed
from something like VBA in the MS Office applications.
Existing Design: Let's call my interface library as Interface.dll. There
are a few dependencies for this Interface.dll. Lets call them as:
MyTypeLib.dll, MyHelper1.dll, MyHelper2.dll and few more helpers.
My approach was:
Develop a new library that has a COM visible class. I did something like:
[ComVisible(true)]
[ClassInterface(ClassInterfaceType.AutoDual)]
[Guid("A023101A-D9B3-4A24-AAE4-B3CFEDA04BAF")]
public class MyCOMVisibleClass
...
...
and selectively call methods from Interface.dll, making these selected
methods COM visible. Let's say above class produces
MyCOMVisibleClassLib.dll. I used RegAsm.exe to register this library and
to produce MyCOMVisibleClassLib.tlb file.
To test this implementation, I decided to use MS Excel 2010. I opened VBA
editor and added a reference to MyCOMVisibleClassLib.tlb. In the code, I
can now see all the methods in MyCOMVisibleClass so it seems to be working
until.....
I ran this code and got "Run-time Error -2146233088 (80131500). Unable to
find MyTypeLib.dll" I used Assembly Binding Log Viewer to see more details
of this error and found that MS Excel was looking for this (MyTypeLib.dll)
everywhere except where actually this file is. If I copy this file into
Excel installation folder under Program Files, Excel would compain about
next dependency - MyHelper1.dll and so on. After I copied all the dlls to
Excel install folder all was good. But this is not the solution I am
looking for.
Questions:
Is my approach correct to open up few methods to COM?
I think that MyCOMVisibleClassLib.dll is the only one that needs to be
registered. Am I right in thinking so?
How do I make Excel to find all my dependencies (MyTypeLib.dll,
MyHelper1.dll, MyHelper2.dll ) without having to copy them in MS Excel
install folder?
I also think that I am missing something basic that I should have known
before I start this but can't seem to figure it out.
Any help is very much appreciated. Thanks in advance.