Dynamic change Sampling per Frame in TI C6000 Embedded Targets

Hallo, in some reason im doing a project witch request dynamic changed sampling per frame. I'm currently using C6455 DSK with Embedded Coder from Simulink. The Background is that, i'm going to make an Application that user can change the FFT length through UDP, and the C6455 DSK will give the new Spectrum with specific FFT-Length recieved from FFT. How can i do that? (Think that the sample per Frame from ADC is 256, it must use ADC to recieve the signal)