Alberto,
it is much more easier for us - the community - if you prevent more information on your questions. In this case, without any codefragment, it is really hard to see what happend....
or, at least the bal file. BUT with just the bal file WE have a LOT work to get a new example created and adding your bal to it... Always better is to post a complete project together with a description where the problem is. At least to whom who want help
so let's think about this, when the compiler says "'(' expected", I would count all (( and )) on the other side and then it should be the same amount of ( and ) on both sides...