Defining a Macro

["Abdel Kader Diagne" <diagne@dfki.uni-sb.de>]

I am trying to define a macro to construct expressions like

     '(fcn-1 [arg1-val [arg2-val]]) 

where arg1-val and arg2-val are (the values of) the arguments of the macro.

I think, the usual way to do it is defining a macro like

(defmacro BUILD-MY-EXPRESSION (arg1 arg2)
  `'(fcn-1 [,arg1 [,arg2]]))

But that doesn't work: the evaluation of the form 
 (BUILD-MY-EXPRESSION 'test1 'test2) returns (FCN-1 [,ARG1 [,ARG2]]) instead of
  (FCN-1 [TEST1 [TEST2]]).

I suppose it is due to the fact that #\[ is a macro-character associated to a
specific function. If so, is there a way to use it locally as a usual char?

Reformulation of the problem:
  I would like to define a macro that returns the same expression as the function 
  defined below:
  
(defun BUILD-MY-EXPRESSION (arg1 arg2)
  (let ((my-expr 
	 (format nil "(fcn-1 [~a [~a]])"arg1 arg2)))
    my-expr))

 Any clue ?

I'll be grateful on any help.
Thanks in advance.

--akd.