书上的习题，快递支付
Private Sub Command1_Click()

Select Case txt.Text
Case Is = ""
lbl.Caption = "请输入重量"
Case Is > 3
lbl.Caption = "请支付" & Val(txt.Text) + 2 & "元"
Case Is = 0
lbl.Caption = "别开玩笑了，请输入重量"
Case Else
lbl.Caption = "请支付5元"
End Select
End Sub

输入10以下数字正常，10以上数字，一律5元，为什么？