无法在中断模式下执行宏

我正在尝试编写一个简单的宏来将单元格的当前值加 1：

Sub add()
    MsgBox Selection.Value
    Selection.Value = Selection.Value + 1
End Sub

当我单击（数字）单元格并尝试运行宏时，我收到以下错误消息：

Cannot Execute in Break Mode

我缺少什么？

You are already executing a macro and somehow stopped its execution (e.g. due to an unhandled error or because you pressed Ctrl-Break during the execution). In this state, you cannot execute another macro.

In the Visual Basic Editor, you need to press the Stop button:

然后就可以运行宏了。

If you want to understand where the current execution is stopped, right click the code and select Show Next Statement. If you then press F8 you can step through the code. F5 continues the execution.