Switch Formula error

Hi, Im having issues with using the Switch formula, below is my expressions if someone could please help?

=SWITCH(
Fields!FiscalMonth.Value = 1 , SUM(Fields!aValue1.Value),
Fields!FiscalMonth.Value = 2 , SUM(Fields!aValue1.Value,Fields!aValue2.Value),
Fields!FiscalMonth.Value = 3 , SUM(Fields!aValue1.Value,Fields!aValue2.Value,Fields!aValue3.Value),
Fields!FiscalMonth.Value = 4 , SUM(Fields!aValue1.Value,Fields!aValue2.Value,Fields!aValue3.Value,Fields!aValue4.Value),
Fields!FiscalMonth.Value = 5 , SUM(Fields!aValue1.Value,Fields!aValue2.Value,Fields!aValue3.Value,Fields!aValue4.Value,Fields!aValue5.Value),
Fields!FiscalMonth.Value = 6 , SUM(Fields!aValue1.Value,Fields!aValue2.Value,Fields!aValue3.Value,Fields!aValue4.Value,Fields!aValue5.Value,Fields!aValue6.Value),
Fields!FiscalMonth.Value = 7 , SUM(Fields!aValue1.Value,Fields!aValue2.Value,Fields!aValue3.Value,Fields!aValue4.Value,Fields!aValue5.Value,Fields!aValue6.Value,Fields!aValue7.Value),
Fields!FiscalMonth.Value = 8 , SUM(Fields!aValue1.Value,Fields!aValue2.Value,Fields!aValue3.Value,Fields!aValue4.Value,Fields!aValue5.Value,Fields!aValue6.Value,Fields!aValue7.Value,Fields!aValue8.Value),
Fields!FiscalMonth.Value = 9 , SUM(Fields!aValue1.Value,Fields!aValue2.Value,Fields!aValue3.Value,Fields!aValue4.Value,Fields!aValue5.Value,Fields!aValue6.Value,Fields!aValue7.Value,Fields!aValue8.Value,Fields!aValue9.Value),
Fields!FiscalMonth.Value = 10 , SUM(Fields!aValue1.Value,Fields!aValue2.Value,Fields!aValue3.Value,Fields!aValue4.Value,Fields!aValue5.Value,Fields!aValue6.Value,Fields!aValue7.Value,Fields!aValue8.Value,Fields!aValue9.Value,Fields!aValue10.Value),
Fields!FiscalMonth.Value = 11 , SUM(Fields!aValue1.Value,Fields!aValue2.Value,Fields!aValue3.Value,Fields!aValue4.Value,Fields!aValue5.Value,Fields!aValue6.Value,Fields!aValue7.Value,Fields!aValue8.Value,Fields!aValue9.Value,Fields!aValue10.Value,Fields!aValue11.Value),
Fields!FiscalMonth.Value = 12 , SUM(Fields!aValue1.Value,Fields!aValue2.Value,Fields!aValue3.Value,Fields!aValue4.Value,Fields!aValue5.Value,Fields!aValue6.Value,Fields!aValue7.Value,Fields!aValue8.Value,Fields!aValue9.Value,Fields!aValue10.Value,Fields!aValue11.Value,Fields!aValue12.Value))