Invalid Function while using setq

[sapsi]

Hello,
I have the following function in my .emacs (or rather Preferences.el
on Aquamacs)

 (defun send-to-R-app ()
        (interactive)
  "Sends the selection to R.App"
  (let ( (myStr2 nil) (mystr nil))(
                (setq mystr (buffer-substring-no-properties (mark) (point)))
                (setq myStr2 (replace-regexp-in-string "\"" "'" mystr ) )
                (do-applescript (concat "tell application \"R\" \r"
                       "cmd "
                        "\"" myStr2 "\""
                       "\r"
                       "end tell"
                       ))
                ) ))
  (global-set-key (kbd "A-r")
                   'send-to-R-app)

When i start emacs, i get this error
 `(setq mystr (buffer-substring-no-properties (mark) (point)))' is a
malformed function.

I have no idea why, also if select the code fragement and type M-x
eval-region and then select some code and type M-x send-to-R-app, i
get a similar error
Invalid function setq mystr (buffer-substring-no-properties (mark)
(point)))

Could someone help me out on this?
Thank you
Saptarshi