adetes3,
Okay, I think I understand what you are trying to do now. You want to browse (much like File->Open) for a part/assembly, if that part/assembly has parameters that match the names in Excel, then copy the values inside Excel to the corresponding part/assembly parameters. Is that accurate?
You could write this for use within the Inventor API or Excel API, it just depends on how you want the end user to interface with the parts/assemblies. You have to ask yourself one important question which will govern whether you create the VBA script for use inside of Excel or Inventor--"Do I want to update the parameters of numerous files quickly and efficiently using a master Excel spreadsheet or do I want to open the part/assembly within Inventor and then browse for the Excel file to update my parameters?"
If you're trying to update a lot of files in a short amount of time then I would choose to write the code for use inside of Excel in which you would fill out your "inputs" sheet, run the script, browse for file, let code update file if applicable, change your inputs, browse for a different file, let the code update that file, and so on. You wouldn't have to even see the file being opened which could allow for very fast performance.
If you're design flow is to create a new part/assembly from a template, which had generic values for the desired parameters, and then update those parameters using your Excel spreadsheet (in which you would edit before running the code) then I would write the code for use within Inventor.
Once you've figured out how you want the user to interact with the part/assembly and what performance you'd like, then you'll know which route to take. Let me know and we can try to figure something out.
Regards,
Trevor