help get around a null value with an if statement.

Below is a some code that performs a calculation. The problem I am having is that there are some null values.  I'm not sure how to write the code and where to place it that will skip to the next record

I think it should be something like this.
If IsNull(Culture_Days) Then
   goto MoveNext
            End If

Could anyone help
Private Sub CmdCvc2_Click()
   
    Dim dblDays As Double
    Dim dblVolume As Double
    Dim dblVCC As Double
    Dim dblCVC As Double
    Dim cn As New ADODB.Connection   'only one DIM per line, it is easier to read
    Dim rst As New ADODB.Recordset
    Dim LinkCriteria As String
    Dim Culture_Days As String

    'Object MUST always be initialized before they can be used
    Set cn = CurrentProject.Connection
    Set rst = New ADODB.Recordset
   
     DoCmd.Hourglass True
     If IsNull(CboSpinner) Or CboSpinner = "" Then
        MsgBox "Please select a Batch from the drop-down list.", , "Missing Spinner Information"
        Exit Sub
    End If
    LinkCriteria = ""
        LinkCriteria = "[sns_ID] = " & CboSpinner
        Debug.Print LinkCriteria

    With rst
                .Open "SELECT * FROM tbl_U2_Spinners WHERE [SpinnerID] =   " & [sns_ID] & "  ORDER   by culture_Days", _
            cn, _
            adOpenKeyset, _
            adLockOptimistic
           
                Do Until rst.EOF
                dblCVC = (dblDays - rst!Culture_Days) _
                    * (dblVolume * dblVCC + rst!Volume * rst!Viable) _
                    / 10 _
                    / (dblVolume + rst!Volume) _
                    + dblCVC

            'if you don't want to update the table then don't do it :)
            'rst!CVC = dblCVC
             'rst.Update
           
           
            dblDays = rst![Culture_Days]
            dblVolume = rst!Volume
            dblVCC = rst!Viable
            rst.MoveNext
        Loop

     rst.Close
   Set rst = Nothing
   Set cn = Nothing
    'Me.CVC = dblCVC
End With
End Sub