I can not belive that you found that out but oh well
What's that supposed to mean?
I wasn't saying you can specify a particular executable, the main thing I was saying was that you can give a blank entry for the executable.
If you know the internal name of the file, winword for example, you can do this:
Winword "%path%\%file%"
Which would open the chosen file with Microsoft word.
Winword, Excel, Powerpnt, and so forth only work without an explicit path because the installer creates a new AppPath entry in the registry.
For example, even with the internal name of a program that doesn't, say, Visual Basic 6 (VB6.EXE), trying to run "VB6" on the command line won't work.
Almost all Office programs implement the addition to the appPath key (SOFTWARE\Microsoft\Windows\CurrentVersion\App Paths), and many other programs do. But, if ever this method fails, the reason is that the executable is not in the AppPaths key.