当必须填写单元格A非空单元格b时的消息框-当前总是显示消息框

Question

我对VBA还是很陌生，我有一个XLS模板，我试图在其中构建消息框，以便用户在模板允许之前在A列中的单元格不为空的情况下强制填写B列中的单元格保存。当前，无论单元格是否为空白，它都会弹出一条消息，一旦单击“确定”，它仍然会保存。有没有建议修改下面的代码以执行所需的操作？

Private Sub Workbook_BeforeSave(ByVal SaveAsUI As Boolean, Cancel As Boolean)

Sub Check()
    Dim rng As Range
    Dim i As Long

    'Set the range in column A you want to loop through
    Set rng = Range("A1:A10000")
    For Each cell In rng
        'test if cell is empty
        If cell.Value <> "" Then
            MsgBox "Cell in column B requires user input in the format of PH_PSIxxxxxx"
            Cancel = True
        End If
    Next
End Sub