error: i is not constant

Basically i would like to divide the total no. of bits entered by user into several block of 8 bits.

e.g 12 bits entered by user. Then it will divide it to out0[7:0] and out1[3:0].

In this case i use memory.

module

....

input [63:0] out_pin_in;

reg [7:0] out_reg [7:0];

...

always (*)

for (i=0; i<8; i= i+1)

begin

if (ocount_e >= 8)

begin

out_reg[i] <= out_pin_in[((i*8)+7):i*8)];

end

end

...

However, i faced a error "i is not constant". I can pretty sure that the font i bold have problem. But i have no clue to solve it. Can somebody help on it? Thanks