File path error in Applescript/TextExpander
I might be totally off track, but give this a try:

tell application "Finder"
    activate
    set f to "Users/MrT/Dropbox/School/Hardvard/6-Fall Session 2013"
    set a to POSIX file f
    open a
end tell


If that fails to work, change it to the following:

tell application "Finder"
    activate
    set f to "Macintosh HD:Users:MrT:Dropbox:School:Hardvard:6-Fall Session 2013"
    set a to POSIX file f
    open a
end tell