Create Dynamic header and footer in Dataport

Hi experts,

Please how can I create a header in my data port that can get dynamic information from my DataItem, i tried with this snippet of code in OnPreDataItem() Trigger but it does'n't work, and the same For my footer in the end i want to get some thing like this

xxxxxxxxx    header

yyyyyyyyyyyyyyyyyyyyyyyyyyyyyyy

yyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyy     Content

yyyyyyyyyyyyyyyyyyyyyyyyyyyyyyy

zzzzzz  Footer

Documentation()

Base Salaire - OnPreDataItem()

CurrFile.TEXTMODE(TRUE);
CurrFile.WRITE('10000000000000000000'+"TableFieldX"+'115000MAD2');
CurrFile.TEXTMODE(FALSE);

Base Salaire - OnBeforeExportRecord()

Base Salaire - OnAfterExportRecord()

CurrFile.TEXTMODE(TRUE);

CurrFile.WRITE("yyyyyy");

CurrFile.TEXTMODE(FALSE);

Base Salaire - OnBeforeImportRecord()

Base Salaire - OnAfterImportRecord()

Base Salaire - OnPostDataItem()

CurrFile.TEXTMODE(TRUE);

CurrFile.WRITE('10000000000000000000'+"TableFieldX"+'115000MAD2');
CurrFile.TEXTMODE(FALSE);