There's no need to automate Calc (or LO)
simply create a file
name it something like 'autostartLibreoffice.bat'
(or anything else, as long as the name ends in '.bat'
The contents of this file should be the names of the files you want to be opened.
so, something like (other locations are OK too ;):
"C:\Users\Luuk\My Documents\TEST1.ods"
"C:\Users\Luuk\My Documents\TEST1.odt"
When you doubleclick the 'autostartLibreoffice.bat' file it will open the 'TEST1'-document, and the 'TEST1'-calcsheet.