Create a New Space in Mavericks using Applescript
delay 0.5 -- time to release command if the script is run with command-R
tell application "System Events"
    key code 126 using control down -- control-up
    delay 1
    do shell script "MouseTools -x 1900 -y 60;sleep 1;MouseTools -leftClickNoRelease;MouseTools -releaseMouse"
    key code 53 -- escape
end tell


You can download MouseTools from http://www.hamsoftengineering.com/codeSharing/MouseTools/MouseTools.html. See http://osxnotes.net/applescript.html for a list of key codes.