MS Access 2013这些代码有什么问题？

Question

我在互联网上找到了这些代码并将它们放在表格上。它似乎很好地工作除了一件事：它一直告诉我“你已经放错了表达式...”如果我不进行计算（默认情况下，该字段是从其他2个字段自动计算的）。请有人告诉我代码有什么问题？感谢

    Private Sub Form_KeyDown(KeyCode As Integer, Shift As Integer)
    Dim varNewValue As Variant
    Dim strErr As String
    On Error GoTo SkipOut
    ' to use the '=' use this line
    'If KeyCode = 187 And Shift = 0 Then
    'To use the Enter Key (my favorite) use this line
    If KeyCode = 13 And Shift = 0 Then
    If Me.ActiveControl.ControlType = acTextBox Then
    If Me.ActiveControl.DecimalPlaces <> 255 Then
    varNewValue = Eval(Me.ActiveControl.Text)
    Me.ActiveControl.Text = varNewValue
    KeyCode = 9
    End If
    End If
    End If
    Exit Sub
    SkipOut:     strErr = Error(Err)
    On Error Resume Next
    KeyCode = 9
    MsgBox Left(strErr, InStr(strErr & "@", "@") - 1)
   Exit Sub
   End Sub