Absolute path to an application executable in OS X
The absolute path to the Adobe Reader executable is:

/Applications/Adobe Reader.app/Contents/MacOS/AdobeReader


Note the space in Adobe Reader and spaces either need to be escaped with a backslash.

/Applications/Adobe\ Reader.app/Contents/MacOS/AdobeReader


Or quote the fully qualified pathname, but not both.

"/Applications/Adobe Reader.app/Contents/MacOS/AdobeReader"


You'll have to test to see which form Excel will work with.

You can view the contents of a application bundle by a ctrl-click (right-click) on the application and select "Show Package Contents", then navigate to the Contents &gt; MacOS folder where the applications executable is.

For Preview its: /Applications/Preview.app/Contents/MacOS/Preview