VBA嵌套IF语句

Question

I want to show a message box when a specific cell has a particular value in it. I have done this with the following code;

If Range("P8") = "Y" Then
        MsgBox "Message here"
End If

This is within the Worksheet_Change sub so shows the message box everytime another cell value changes. I have tried to get around this by adding a boolean variable, set to true when the messagebox has been shown the first time;

If Range("P8") = "Y" Then
    If messageshown = False Then
        messageshown = True
        MsgBox "Message here"
    Else
    End If
Else
End If

However the message box still shows every time I change a cell in the worksheet. I have a feeling it';s to do with the way I have written the nested if statement but have tried various different ways and orders of where I place else and end if but to no avail.

Answer 1

Use the Target argument instead - this refers to the actual cell being changed, which is what you are interested in. Test the address of the Target to see if it's the cell you need and then act accordingly. This will stop the message showing when another cell is changed.

Private Sub Worksheet_Change(ByVal Target As Range)
    With Target
        If .Address = "$P$8" And .Value = "Y" Then MsgBox "Message here"
    End With
End Sub

Answer 2

Try this code, it first checks which cell is changed, if it is anything but P8, it will not pop the messagebox.

Private Sub Worksheet_Change(ByVal Target As Range)
    If Target.Address = "$P$8" Then
        If Range("P8") = "Y" Then
            MsgBox "This works"
        End If
    End If
End Sub

As pointed out by Macro Man, there is a more optimal, more efficient option.