case () inside gives errors with ncvlog

case(ratio)inside[990:1010]:  mon_txn.bit_rate_captured  =3'b000;[390:410]:  mon_txn.bit_rate_captured  =3'b001;[190:210]:  mon_txn.bit_rate_captured  =3'b010;[90:110]:  mon_txn.bit_rate_captured  =3'b011;[35:45]:  mon_txn.bit_rate_captured  =3'b100;[16:24]:  mon_txn.bit_rate_captured  =3'b101;[8:12]:  mon_txn.bit_rate_captured  =3'b110;endcase

(1)case (ratio) inside 

   ncvlog: *E,ILLPRI: illegal expression primary [4.2(IEEE)]

(2) [990 : 1010] :  mon_txn.bit_rate_captured  = 3'b000;

	               |

    ncvlog: *E,NOTSTT : expecting a statement [9(IEEE)]

(3) [390 :410]   :  mon_txn.bit_rate_captured  = 3'b001;

	     |

     ncvlog: *E,ILLPRI : illegal expression primary [4.2(IEEE)].

(4)  [390 :410]   :  mon_txn.bit_rate_captured  = 3'b001;

	             |

      ncvlog: *E,NOTSTT : expecting a statement [9(IEEE)].

and so on