Error in shift operator

Hello:

I have this error in my verilog  code:

1

 case (aexp[14] ^ bexp [14])

2

3

        1'b0 :   bman = bman << (aexp- bexp);

4

        1'b1 :   bman = bman << (aexp+ bexp);

5

6

       endcase

here, if the sign bit [14] is equal, so sub aexp - bexp then shift the 
bman by the difference.
or if they are not equal so add them and shift.

but in my simulator I cant see bman shift at all, so i change the code 
to :

1

 case (aexp[14] ^ bexp [14])

2

3

        1'b0 :   diff = bman << 3;//(aexp- bexp);

4

        1'b1 :   diff = bman << 2;//(aexp+ bexp);

5

6

       endcase

also there is no value in diff !!
could you please help me
thanks