Due to an update in the Quartus® II software v15.0 release, the above command is no longer functional, even though it still shows in the handbook.
The handbook describes using "dspba.set_param(control{1},\'destination\',dest_dir)" to change the RTL destination directory.
To change your RTL destination directory in the Quartus® II software v15.0 and later, use the following command:
dspba.SetRTLDestDir(model,dest_dir)
For example, if you are using the demo_fft.mdl example that comes with the DSP Builder for Intel® FPGAs (Advanced Blockset), use the following command:
dspba.SetRTLDestDir(\'demo_fft\',\'MyRTL\')