in a bat file you can put this line
start /min "" "E:\work\MyData\file1.xlsx"
start /min "" "C:\Downloads\file2.xls"
start /min "" "D:File3.xlsx"
or if all files are in a single folder on disk, you can use loop
for %%1 in (File1.xlsx File2.xls File3.xlsx) do (start "" "E:\MyData\%%1")
For this to work, you should already have attached xlsx and xls extenstions to MS Excel in defaults programs, which normally already happens at MS Office install.
then put a shortcut to this bat file on your desktop, once you reach desktop double click to run that, no UAC required, and all files will go on opening one by one minimized and you can do your other work in between.
or if you want that to be run automatically at each boot, put the bat file shortcut in shell:startup folder.