Reporting Services :: Getting Error Displayed When Using InStr

I have a field that contains a town  ex : New York. Sometimes, the field will have brackets to be more specific ex: New York (Brooklyn). What I need is a formula that will return only "Brooklyn" if there are brackets or  the whole field if there are no brackets.Here's what I thought would do the trick :

=Iif(InStr(First(Fields!Ville.Value, "MW1R017A_IdentificationTravailleur_AdresseTravailleur"), "(") > 0,
Left(Split(First(Fields!Ville.Value, "MW1R017A_IdentificationTravailleur_AdresseTravailleur"), "(")(1), len(Split(First(Fields!Ville.Value, "MW1R017A_IdentificationTravailleur_AdresseTravailleur"), "(")(1)) - 1)
, First(Fields!Ville.Value, "MW1R017A_IdentificationTravailleur_AdresseTravailleur"))

So if InStr returns more than 0, meaning that I have brackets, I'll split at the "(", get the second part and remove the last character which is the closing bracket I don't want. If there is no bracket, I'll return the whole field.Somehow, when there is no bracket, my report overview shows me "#Error" as if the first Iif was true and what's in the true part is not actually possible, because it's trying to take the second part of a split that couldn't split because there is no bracket to split.