UC_OBJECTS not convertible

hello, i am a bi developer and have to write badi to extract data from a table called ZNetSOME. I want to populate 2 fields in my structure "C_T_DATA". Those fields are ZOrder and ZAmount. here is the code that I wrote but keep getting u_c_objects_not_convertible message.i am not an abaper so your help will be very appreciated.

DATA: IT_ZNETSOME TYPE TABLE OF ZNETSOME,

WA_ZNETSOME TYPE ZNETSOME.

DATA: WA1_ZNETSOME TYPE ZNETSOME.

LOOP AT C_T_DATA INTO WA_ZNETSOME.

SELECT SINGLE * FROM ZNETSOME INTO CORRESPONDING FIELDS OF WA1_ZNETSOME WHERE ZORDER = WA_ZNETSOME-ZORDER.

WA_ZNETSOME-ZORDER = WA1_ZNETSOME-ZORDER.

WA_ZNETSOME-ZAMOUNT = WA1_ZNETSOME-ZAMOUNT.

ENDLOOP.

I would also need to do

APPEND C_T_DATA FROM WA_ZNETSOME to populate the values in C_T_DATA structure but it keeps giving me out error

"An explicit work area is necessary in the OO context. Use "APPEND wa TO C_T_DATA [SORTED BY]".

thanks.

please help me out.