Facing Security permission preview rdl report

Question

I am working on an application facing a security permission issue while wanting to preview a report using view report. Below are the expressions I am using in grpAccountCat are given below.

Filter Expression

=IIF((SUM(Fields!NatlAmount.Value) = 0) AND (SUM(Fields!NatlYTD.Value) = 0) AND (Parameters!ExcludeZeroBalance.Value = True), False, True)

Variables

=Code.SetTot(Fields!accountcat.Value, SUM(Fields!Amount.Value))

Below is the function I have defined in the Code tag on "rdl" XML

<Code>
Function SetTot(Type As String, Value as Decimal) As Decimal
    Dim ret as Decimal = 0
    
    Select Case Type.ToLower()

    Case "eq"
        EQTot = Value
    Case "ex"
        EXTot = Value
    Case "cs"
        CSTot = Value
    Case "ot"
        OTTot = Value
    Case "rv"
        RVTot = Value
    End Select

    ret = Value

    return ret 
End Function

</Code>

The error is shown in the below image while trying to view the report.