Invalid Use of Default Parameter Error While Performing an Insert

Question

I get an error thrown when I try to execute my command to insert a new row into my database. I believe the error is being thrown by Null values. Although I cannot be sure about that.

Here is my code:

Sub AddRows()

Dim Cn As ADODB.Connection
Dim Server_Name As String
Dim Database_Name As String
Dim User_ID As String
Dim Password As String
Dim SQLStr As String  

Dim comm As ADODB.Command
Set comm = New ADODB.Command
Dim param As ADODB.Parameter
Dim getType As MultipleValues
Dim nullCheck As String

SQLStr = "Insert Into [Steve_Dev_Matrix] Values("
For i = 1 To 121
    'Get type
    SQLStr = SQLStr & "?,"
    Set param = New ADODB.Parameter
    param.Name = "Param" & i
    Set param = comm.CreateParameter("param" & i, CLng(CellType(i, Cells(2, i).Value).CellType), adParamInput, CellType(i, Cells(2, i).Value).CellNum)
    param.Attributes = adParamNullable
    'Debug.Print (param.Type)
    comm.Parameters.Append param
Next i
SQLStr = Left(SQLStr, Len(SQLStr) - 1) & ");"

Set Cn = New ADODB.Connection
Cn.CommandTimeout = 0
Cn.Open "Driver={SQL Server};Server=" & Server_Name & ";Database=" & Database_Name & _
";Uid=" & User_ID & ";Pwd=" & Password & ";"

comm.ActiveConnection = Cn
comm.CommandText = SQLStr
comm.CommandType = adCmdText


Dim test As String
lastrow = Sheet1.Cells(Sheet1.Rows.Count, "A").End(xlUp).Row
'For x = 2 To lastrow
    For i = 1 To 121
        Debug.Print (comm.Parameters.Item("Param" & i).Type)
        comm.Parameters.Item("Param" & i).Value = Cells(2, i).Value
    Next
    comm.Execute

 '            Tidy up
Cn.Close
Set Cn = Nothing
End Sub

Also here is an example of the CellType method:

Private Function CellType(Num, Rng) As MultipleValues
Application.Volatile
Select Case True
    Case Num = 1
        CellType.CellType = adInteger
    Case Num = 2
        CellType.CellType = adInteger
    Case Num = 3
        CellType.CellType = adVarWChar
        CellType.CellNum = 255
    Case Num = 4
        CellType.CellType = adCurrency
    Case Num = 5
        CellType.CellType = adVarWChar
        CellType.CellNum = 255

The error says: Invalid use of default parameter