Output value doesn't change for different inputs to muPad procedure

I am using MATLAB procedures to generate a 1024 bit number randomly. I am using this code for it.

z:=26;num:=1;
while z>0 do
  num:=num*random();
  z:=z-1;
end_while;

Thus, 'num' will be random()^26.

I call this procedure in my MATLAB code. Since 'num' is a random number it should change every time i call the procedure. But it doesn't. I get only one value for 'num' always.

Where am I going wrong? And how can i correct it?

Thank you for your time and help.