Why are you adding parenthesis? Why did you change the single quotes to double quotes? eriqjaffe's sample code was correct as posted!

Review the readme/active help for robocopy and the Kix manual for the Shell command to make sure your syntax is correct.

Anytime you have spaces in filenames, they must be surrounded in quotes. Kix treats single and double quotes alike, but DOS commands generally REQUIRE double quotes to be happy. Thus, you use Single quotes to define the Kix command, and double quotes inside the single quotes to encapsulate the paths.
 Code:
shell 'robocopy sourcepath "dest path with spaces" /E'
Note the single quotes to delimit the ENTIRE shell command, and the double quotes to delimit only the "path with spaces".

Glenn
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Actually I am a Rocket Scientist! \:D