Public Function Custom Code SSRS 2014

I'm trying to convert a 2005 .rdlc to a 2014 .rdl. There is custom code that no longer works after the conversion. One field would have code snippets for it like this in the code: <Textbox Name="textbox9"> <Value>=Code.GetSubTotal(Sum(Fields!extended.Value))</Value>Public Shared _subtotal as Double Public Function GetSubTotal(ByVal subtotal as Double) _subtotal = subtotal End FunctionMy question is, since this returns nothing to the report, is this function even performing, well, any function?What would be a better way to get fields like this returned to the report?Thank you!!