Error while execute Custom Code in RDLC

="Amount in words: " & Code.changeToWords(CStr(FormatNumber(Sum(Fields!dTurnover.Value),2)))

Actually my custom code accepts string value as parameter.

Public Function changeToWords(ByVal numb As [String]) As [String]
Dim numb as string = Convert.toString(val)
Dim val As [String] = ""
Dim wholeNo As [String] = numb
Dim points As [String] = ""
Dim andStr As [String] = ""
Dim pointStr As [String] = ""
Dim endStr As [String] = "Only"
Dim decimalPlace As Integer = numb.IndexOf(".")
If decimalPlace > 0 Then
wholeNo = numb.Substring(0, decimalPlace)
points = numb.Substring(decimalPlace + 1)
If Convert.ToInt32(points) > 0 Then
andStr = "and"
pointStr = translateCents(points)
pointStr= pointStr & " Paise "
End If
End If
val = [String].Format("{0} {1}{2} {3}", translateWholeNumber(wholeNo).Trim(), "Rupees " & andStr, pointStr , endStr)
Return val
End Function

Private Shared Function translateWholeNumber(ByVal number As [String]) As [String]
Dim word As String = ""
Dim beginsZero As Boolean = False
Dim isDone As Boolean = False
Dim dblAmt As Double = (Convert.ToDouble(number))
If dblAmt > 0 Then
beginsZero = number.StartsWith("0")
Dim numDigits As Integer = number.Length
Dim pos As Integer = 0
Dim place As [String] = ""
Select Case numDigits
Case 1

word = ones(number)
isDone = True
Exit Select
Case 2

word = tens(number)
isDone = True
Exit Select
Case 3

pos = (numDigits Mod 3) + 1
place = " Hundred "
Exit Select

Case 4, 5, 6
pos = (numDigits Mod 4) + 1
place = " Thousand "
Exit Select

Case 7, 8, 9
pos = (numDigits Mod 7) + 1
place = " Million "
Exit Select
Case 10

pos = (numDigits Mod 10) + 1
place = " Billion "
Exit Select
Case Else

isDone = True
Exit Select
End Select

If Not isDone Then
word = translateWholeNumber(number.Substring(0, pos)) + place + translateWholeNumber(number.Substring(pos))

If beginsZero Then
word = " and " & word.Trim()
End If
End If

If word.Trim().Equals(place.Trim()) Then
word = ""
End If
End If

Return word.Trim()
End Function

Private Shared Function tens(ByVal digit As [String]) As [String]
Dim digt As Integer = Convert.ToInt32(digit)
Dim name As [String] = Nothing
Select Case digt
Case 10
name = "Ten"
Exit Select
Case 11
name = "Eleven"
Exit Select
Case 12
name = "Twelve"
Exit Select
Case 13
name = "Thirteen"
Exit Select
Case 14
name = "Fourteen"
Exit Select
Case 15
name = "Fifteen"
Exit Select
Case 16
name = "Sixteen"
Exit Select
Case 17
name = "Seventeen"
Exit Select
Case 18
name = "Eighteen"
Exit Select
Case 19
name = "Nineteen"
Exit Select
Case 20
name = "Twenty"
Exit Select
Case 30
name = "Thirty"
Exit Select
Case 40
name = "Fourty"
Exit Select
Case 50
name = "Fifty"
Exit Select
Case 60
name = "Sixty"
Exit Select
Case 70
name = "Seventy"
Exit Select
Case 80
name = "Eighty"
Exit Select
Case 90
name = "Ninety"
Exit Select
Case Else
If digt > 0 Then
name = (tens(digit.Substring(0, 1) & "0") & " ") + ones(digit.Substring(1))
End If
Exit Select
End Select
Return name
End Function

Private Shared Function ones(ByVal digit As [String]) As [String]
Dim digt As Integer = Convert.ToInt32(digit)
Dim name As [String] = ""
Select Case digt
Case 1
name = "One"
Exit Select
Case 2
name = "Two"
Exit Select
Case 3
name = "Three"
Exit Select
Case 4
name = "Four"
Exit Select
Case 5
name = "Five"
Exit Select
Case 6
name = "Six"
Exit Select
Case 7
name = "Seven"
Exit Select
Case 8
name = "Eight"
Exit Select
Case 9
name = "Nine"
Exit Select
End Select
Return name
End Function


Private Shared Function translateCents(ByVal cents As [String]) As [String]
Dim cts As [String] = ""
Dim digit As [String] = ""
Dim engOne As [String] = ""
Dim i As Integer = 0
For i = 0 To Len(cents) - 1
digit = cents(i).ToString()
If digit.Equals("0") Then
engOne = "Zero"
Else
engOne = ones(digit)
End If
cts = cts & " " & engOne
Next
Return cts
End Function