I need to create a 250x1250 Low Density Parity Check matirx ( LDPC) for a 1000 bit message length in MATLAB.

I need to make a 250x1250 Low Density Parity Check matirx ( LDPC) for a 1000 bit message length. But the Matlab built-in function dvbs2ldpc(r) only create a (64800-message length)x64800 sized parity check matrix. How i can create a low density parity check matirix of arbitrary size ( specially in the range of 250x1250) in Matlab script??