SQ02 syntax error when is processed internal table %dtab

Hi Gurus

I have to insert code in custom infoset from SQ02.

The goal is to modify internal table %DTAB in Code Section END-OF-SELECTION(before List).

Internal table %DTAB is table where are data extracted from SAP tables.

The problem is that i can't declare internal table in code section DATA in this way : data %dtab type standard table of /1BCDWB/IQG000000000026 with header line , because program dumpes at gives to me this error %DTAB" has already been declared.

But if i do not declare the table , when i check syntax error gives to me syntax error field %DTAB is unknown .

Any idea to solve this problem?

Thanks in advance