DFR optimization

Hi,
I'm trying to create a response (frf displacement) for DFR solution, but when I create an objective or dconstraint using this response, I get an error message:

 

Selected subcase ('Name') is not compatible with the type of response.

 

here is the information about subcase and loads:

 

SUBCASE       1
  LABEL DFR_100Hz                                                                       
ANALYSIS DFREQ
  FREQUENCY =      100
  DLOAD =      300

 

---------------------------------------------------------------------------------

 

$$
$$
$$  FREQi cards
$$
$HMNAME LOADCOL              100'Freq_def'
$HWCOLOR LOADCOL             100      23
FREQ         100   100.0
$
$$
$$  RLOAD1 cards
$$
$HMNAME LOADCOL              300'Rload_def'
$HWCOLOR LOADCOL             300      23
RLOAD1       300     400                     200       0        
$$
$$
$$ DAREA Data
$$
DAREA        400    1000       31.0     
$$
$$  TABLED1 cards
$$
$HMNAME LOADCOL              200'Table_def'
$HWCOLOR LOADCOL             200      23
TABLED1      200  LINEAR  LINEAR
+            0.0     1.0  1000.0     1.0ENDT   

 

so, the analysis is ok, but how can i create an optimization for it?

 

Thanks.

 

(P.S. version of optistruct i use is 12 and 13)