Impulse response for FIR filter design
Since the blackman window is defined in relation to its length (at least, that is, with the parameter chosen canonically), there's too few parameters open to match the band edges. You could, however:




Determine $\omega_0 \over \pi$ (the $\pi$ being the scale built in to the $\operatorname{sinc}$ function). $\omega_0$ could be picked as the arithmetic mean of the band edges.

> w0=600/7200
Window a sinc scaled accordingly by a blackman window.

 > F=sinc((-71.5:71.5)*w0)).*blackman(144)'

F now contains a sinc windowed by the blackman function, centered about the middle of the filter (giving a constant phase filter).


The resulting filter is quite steep, but it has a rather leaky stopband. If the task at hand was a different one, please excuse and explain in a little more detail.