Open a command prompt window, run in this window for /? and read very carefully all output help pages.
Command FOR with option /F splits up a string by default on spaces/tabs. It can be either used "tokens=*" or "delims=" to avoid this string splitting. The usage of "delims=*" works also for file names because the name of a file without or with path can't contain an asterisk. But "delims=*" is usually not used to prevent splitting up a string into tokens because a string read from a text file, output of an application or an environment variable could contain 1 or more asterisks as well.
Next run in a command prompt window cmd /? and read at least last output help page on which is explained on which characters in name of a file/folder without or with path the file/folder name string must be enclosed in double quotes. In general it is advisable to enclose file/folder names without/with path always in double quotes.
The command DIR returns with the used options just the names of the files without path and always without surrounding double quotes as it can be seen on running in a command prompt window in directory with Book 1-* files
dir "Book 1-*" /A-D /B /O-D /TW
after first running dir /? to get displayed the help for command DIR.
So used should be:
for /F "delims=" %%# in ('dir "Book 1-*" /A-D /B /O-D /TW 2^>nul') do ( start "" excel.exe "%%#" & exit /B )
2^>nul is 2>nul whereby the redirection operator > is escaped with ^ to apply this redirection on running command DIR instead of being interpreted as redirection of command FOR at an invalid position in command line. The command DIR outputs the error message File not found to handle STDERR if it can't find any file in current directory matching the pattern Book 1-*. This error message is suppressed by redirecting it to device NUL.
It is advisable to specify the application to start with file extension if well known even if the path is not known. Read answer on Where is “START” searching for executables? for an explanation.
In the batch command line above there are after command START also two double quotes before the name of the executable to start. Usage of "" is highly recommended as command START interprets often first double quoted string in arguments list as optional title string. By specifying explicitly an in this case empty title string helps to avoid unexpected application execution. For details on command START run in command prompt window start /?.
And last it is better to use command EXIT with parameter /B to exit just processing of current batch file and not exit entire command process. If this batch file is called with command CALL from another batch file or started from within a command prompt window and command EXIT is used without parameter /B, the processing would not continue on parent batch file respectively command prompt window would be closed by EXIT, too. There is no difference between usage of exit and exit /B if this batch file is executed by a double click on the batch file. For details on command EXIT run in a command prompt window exit /?.
By the way: The command START uses file association registration data if it can find an executable or script with given name to open the specified file with the registered application for the file extension.
So it would be also possible to use:
for /F "delims=" %%# in ('dir "Book 1-*" /A-D /B /O-D /TW 2^>nul') do ( start "" "%%#" & exit /B )
Now command START opens the *.xslx file with whatever application is associated with this file extension as default application for opening it.
