you can automate excel to do what you want, but that is different from shelling the whole thing from the command line
as you know, you can only save 1 sheet to csv, so you can copy that sheet to temp workbook, or delete all other sheets first, when you saveAs the original workbook will be closed with no changes

you can use application.displayalerts = false to stop most warnings, but i doubt that will be satisfactory to avoid warning about too many sheets, there is also option in saveAs
from msdn
SaveAs Method


Saves changes to the sheet (Syntax 1) or workbook (Syntax 2) in a different file.

Syntax 1

expression.SaveAs(Filename, FileFormat, Password, WriteResPassword, ReadOnlyRecommended, CreateBackup, AddToMru, TextCodePage, TextVisualLayout)

Syntax 2
syntax1 is to save a sheet, syntax 2 is to save workbook, the sheet syntax is what you want in this case