Field symbols

Hi Friends,

I have an internal table where I want to assign values into fields as below using field symbols. How do I get the value back into the workarea.

DATA : BEGIN OF it_out OCCURS 0,

m011 TYPE curr_tax_bvl_ly,

m021 TYPE curr_tax_bvl_ly,

m012 TYPE curr_tax_bvl_ly,

m022 TYPE curr_tax_bvl_ly,

m013 TYPE curr_tax_bvl_ly,

m023 TYPE curr_tax_bvl_ly,

END OF it_out.

FIELD-SYMBOLS: <fs_fld> TYPE ANY.

DATA : l_field(15) TYPE c.

CONCATENATE 'it_out-m' '02' '1' INTO l_field.

ASSIGN (l_field) TO <fs_fld>.

<fs_fld> = bsad-wrbtr.

Value of it_out-m021 is still initial ?

Please let me know how to get value into it_out-m021.

Thanks in advance