只是需要一些帮助来理解forloop的实现。
以下是我失败的尝试：

Sub test()

   Do Until IsEmpty(Worksheets("do not open!").Range("F1"))
         If UI.ComboBoxSource <> ActiveCell Then
         MsgBox "This procedure already exhists. Please click on update summary. "
         Else
         End If
         Worksheets("do not open!").Range("F1").Offset(1, 0).Select
         Loop

End Sub

以下是@FaneDuru的正确尝试：

Sub test()
  Dim ws As Worksheet, rngF As Range
  
  Set ws = Worksheets("do not open!")
  Set rngF = ws.Range("F1")
   
   Do Until rngF.Value = ""
         If UI.ComboBoxSource <> rngF.Value Then
            MsgBox "This procedure already exhists. Please click on update summary. "
         Else 
            'do something...
         End If
         Set rngF = rngF.Offset(1)
  Loop

End Sub

我尝试循环遍历一个单元格区域（在本例中，按F1向下，直到空白单元格），并应用if语句比较值是否匹配。如果值匹配，则我希望循环继续，直到结束......如果不匹配，则我希望出现MsgBox并停止循环。
这就是我试图做的：

Sub check_procedures()
  Dim ws As Worksheet, rngF As Range
  
  Set ws = Worksheets("do not open!")
  Set rngF = ws.Range("F1")
   
   Do Until rngF.Value = ""
         If UI.ComboBoxSource = rngF.Value Then
         MsgBox "This procedure already exhists. Please click on Update Summary. "
         Exit Sub
         
         
         Else
         End If
            
            
         Set rngF = rngF.Offset(1)
         
         
    
    Loop
    
End Sub

谢谢你的帮助。