Hi Ivana,
thanks for the fast reply.
My code is like the one above
     case "mymacro":
           match = true;                
           result = GetWhereCondition();
           break;
and then GetWhereCondition() function returns the SQL where condition like :
city='Milan' and nation='Italy'    (it's only for sample)
with debugger result=city='Milan' and nation='Italy'  
but explorer (when I open the page with web part) return an SQL error : incorrect sintax ....
city=''Milan'' and nation=''Italy''      (the ' is changed in '' ) 
best regards
Nicola Cesaroni