Hi Rakesh,
In GNU Radio, FM demodulator is implemented digitally as
a = present_complex_sample * conj(previous_complex_samples)
out[current] = some gain * arctan ( imag(a), real(a) ); //demodulated FM
signal
So, you can also implement the same for demodulating FM signal in
MATLAB.
Recorded FM files may already be available in internet. So, use that
file
and test your MATLAB code.
For connecting USRP to Matlab, toolbox is already released by Mathworks
from 2011 versions. If using older version of Matlab, you can use
Flexible Radio third-party plugins.
But, you can only use RFX 900 board which will not support FM reception
freq.range 
Hope this might help you,
Senthil