What worked for me was using GetObject(,""Excel.Application"") in the code stages that i created in my more specific application to get the excel instance created by the MS Excel VBO.
To add a key to the instance obtained, using the copied global code, the local code would look something like this (assuming you launched the application via MS Excel VBO already and only 1 instance is running):
Dim app As Object
app = GetObject(,""Excel.Application"")
'If you have a data item to store a handle in:
'Optional: handle = GetHandle(app)
There are many other ways to achieve the above.
That way you can also include other actions from the general VBO with a bit of diving into and understanding the code behind.