Typically you do not import data into Excel via the command line.  In over 15
years of using Excel, I cannot recall that I have ever done it that way.  
Obviously that doesn't mean that the ability or use that way is a bad thing,
just not one I've ever used.  I doubt if you have any control over format of
the incoming data at all.

To automate generation of a workbook usually takes a fair amount of VB
coding to locate and open the source file and transfer the data into the
Excel workbook and do things like formatting the data and worksheets, and
even adding new worksheets when required without operator intervention.