Its just this piece of code. I need to concatenate some field names into a string, so the actual code is :

lTempFields=""
FOR i=1 TO lnCampos
IF ASCAN(TblFields, UPPER(This.iaData[i, 1]))>0
zz=ALLTRIM(UPPER(This.iaData[i, 1]))+","

lTempFields=lTempFields+zz
ENDIF
ENDFOR

Tblfields has a =AFIELDS() of my table, so Im getting all the strings in ladata wich have a corresponding field in the table