Switch -Z<file> - read archive comment from file
If this switch is specified with any archive modification command, the archive comment is read from the file and added to archive. Use with -sc switch if you need to specify the character set for comment text file.
add all files from the current folder to the solid archive Receipts with an archive comment from file Receipts.diz
WinRAR a -zReceipts.diz -s Receipts