In reply to Paolo55:
$urandom_range() will only return a 32 bit unsigned integer. If you want to get a larger value, you will need to make several calls to the $urandom_range() function.
bit [95:0] val;
val[31:0] = $urandom_range(32'hffff_ffff, 0);
val[63:32] = $urandom_range(32'hffff_ffff, 0);
val[95:64] = $urandom_range(32'hffff_ffff, 0);
or
val = {$urandom_range(32'hffff_ffff), $urandom_range(32'hffff_ffff), $urandom_range(32'hffff_ffff)};