Error in at line-selection event...

Hello experts,

In my report, I am hiding the values of BUKRS, ANLN1 and ANLN2 during my loop.

I am using field symbols as my work area for my itab which is it_output. The problem

is, when I try to do this in my at line-selection event:

at line-selection.

data: cursorfield(20) type c.

get cursor field cursorfield.

case cursorfield.

when '<FS_OUTPUT>-ASSET_SUBNUM'.

SET PARAMETER ID 'BUK' FIELD <FS_OUTPUT>-bukrs.

SET PARAMETER ID 'AN1' FIELD <FS_OUTPUT>-asset.

SET PARAMETER ID 'AN2' FIELD <FS_OUTPUT>-anln2.

endcase.

It says that it can't recognize the fields. What am I doing wrong? By the way, I am using

ABAP Objects in my report. Help would be greatly appreciated. Thanks again guys and take care!