one additinal note here of what I did:

In order to be able to connect to the Excel File (Excel.xls the sample that has column names) I had to delete the expression of the connection manager and run the package and that's when it worked. After that I added the expression Filepath = @[User::filename] and that's when it didn't allow me to assign the subGroup variable.

In the article at the variable section you are talking about Grouping and subgrouping variables. Are these the User::Group and User::SubGroup variables or there are other ones? I think they are but it is not working.