force evaluation of the first argument of the function with_stdout

Hi,

How can I do force evaluation of the first argument of the function 
with_stdout.

More precisely, I am trying to write a function to write a geomview file 
in order to plot a parametric curve. The code is this:

geomview_curve(list,range,nticks,file_name):=block(
  [t,numer:true,display2d:false],
  with_stdout(file_name,
  print("VECT"),
  print("1 ",nticks," 1"),
  print(nticks),
  print("1"),
  for t:range[2] thru range[3] step (range[3]-range[2])/nticks do
  print( ev(subst(t,range[1],list[1]),float),
    ev(subst(t,range[1],list[2]),float),
    ev(subst(t,range[1],list[3]),float)),
  print("1 0 0 1")
));

For any call, for instance geomview_curve(...,"curva"),
it always write a file named "$file_name" and not "curva".

I have seen a similar question in the mailing list but no answer.

Thanks in advances,
jose cano