Hey Mitchell,
You mention Auto-Hot-Key (a Windows utility), but you haven't told us that you're using Parallels or another virtualization software to access Windows.
You haven't provided a sample of what your Excel workbook looks like.
Alt-Tab is not a native keyboard shortcut on the Mac.
Moving back and forth from Excel to something else is dreadfully inefficient.
Excel is scriptable.
There are some examples of a task similar to yours here.
If you want help please describe your workflow with enough detail that we can help.
-Chris