Please follow the MicroStation Programming forum best practices.
Identify Your Platform
Please identify the version of MicroStation, or other product such as PowerDraft, that you are using: MicroStation CONNECT or MicroStation V8i. What is the 8-digit version number (e.g. 10.xx.yy.zz) of MicroStation?
If you're using MicroStation in a ProjectWise (PW) managed environment, let us know that too.
The APIs supplied with MicroStation CONNECT are different to those supplied with MicroStation V8i. Consequently, our answers are likely to be different.
Please also identify the version of Excel you are using. Is this 32-bit or 64-bit Excel?
Code Syntax Highlighting
When you post code, use the Forum advanced editor's syntax highlighting tool. That's the icon that resembles a pencil: 
Identify Your Programming Language
[quote user="BFrancis"] I am trying to write a small VBC code[/quote]
Can we assume that you're writing a VBA macro?
VBA References
Your VBA project references two libraries: the TriForma VBA lib and Excel 15. That's a very specific setup and hard for anyone else to test without that exact combination of installed products.
Since it's ElementEnumerator that's giving you problems, I suggest that you create a new, simple, VBA project. Write your scanning code in that skinny project. If you need to ask further questions, it will be easier for anyone on this Forum to analyse without external references.
There are examples of ModelRefrence.Scan in MicroStation VBA help, and additional VBA examples on our web site.