不同子程序中全局变量和局部变量的使用

我正在使用 VBA 将粘贴内容从 Excel 复制到 PowerPoint。它正在工作，但我需要清理我的代码。问题是，当涉及在多个过程中使用的变量（或对象）时，我不知道什么是好的做法。我想我在这方面缺乏一些基本的了解。

1. 将变量从一个过程传递到另一个过程时，在两个过程中使用相同的名称是否是一个坏主意？所以例如

   Sub 1()
       Dim a As Long, b As Long
       Call Sub2(a, b)
       '...
   End Sub
   
   Sub2(a As Long, b As Long)
       '...
   End Sub
   

   是否应该Sub2以不同的方式调用变量，例如 x 和 y？如果没有，我将回到问题 1)：直接从Sub1to传递这些变量Sub2而不是全局声明它们的原因是什么？当我打算在调用后使用aand bin的原始值时我得到了它（所以基本上将它作为to传递），但在我的情况下并非如此。Sub1Sub2ByValSub2

2. 是否有理由限制全局变量的使用？我留在了我的代码的地方，但我应该定义lRowAn，lRowData等全球？

3. 我什么时候应该将一个变量从一个 sub 传递给另一个？在我下面的代码中，这样做iSlides对我来说很有意义，但对于wsEm.

   以下是我的实际代码的一部分。SubsEmData和EmDataAn非常相似，我会看看是否可以合并它们，但它们很好地说明了我遇到的问题，因为它们使用了许多相同的变量。

   Public mySlide As PowerPoint.Slide
   Public PowerPointApp As PowerPoint.Application
   Public myPresentation As PowerPoint.Presentation
   Public MonatNum As String, JahrNum As String, MonatStr As String
   
   Sub CreateReport()    
       Dim DestinationPPT As String
       Dim iSlides As Integer
       Dim fRowAn As Long, lRowAn As Long, lRowData As Long
       Dim wbEm As Workbook
       Dim wsEm As Worksheet
   
       Set PowerPointApp = New PowerPoint.Application
       DestinationPPT = "C:\VBA\ReportTemplate.pptm"
       Set myPresentation = PowerPointApp.Presentations.Open(DestinationPPT)
   
       Set wbEm = Workbooks.Open("C:\VBA\Report.xlsx")
       Set wsEm = wbEm.Sheets("Sheet1")
   
       lRowAn = wsEm.Cells(Rows.Count, 3).End(xlUp).Row
       fRowAn = wsEm.Cells(Rows.Count, 3).End(xlUp).End(xlUp).Row + 1
   
       If lRowAn >= 127 Then
           If lRowData <= 127 Then '4 Slides, but separate Annotations from Data
               iSlides = 1
               Call EmData(wsEm, iSlides)
               Call EmDataAn(wsEm, iSlides)
           Else '4 Slides
               iSlides = 3
               Call EmData(wsEm, iSlides)
           End If
       Else '3 Slides
           Call EmData(wsEm, iSlides)
       End If
   
       Application.DisplayAlerts = False
       wbEm.Close SaveChanges:=False
       Application.DisplayAlerts = True
   
       PowerPointApp.Visible = True
       PowerPointApp.Activate
       Application.CutCopyMode = False
   End Sub
   
   
   
   Sub EmData(wsEm As Worksheet, iSlides As Integer)
       Dim i As Integer
       Dim fRowDataCalc As Long, lRowDataCalc As Long, lRowCopy As Long
       Dim rowHght As Long
       Dim rng As Range
   
       For i = 0 To iSlides
           fRowDataCalc = 4 + 40 * i + i * 1
           lRowDataCalc = 4 + 40 * (i + 1) + i * 1
   
           With wsEm
               .Range("B2:K3").Copy .Range("B500")
               .Range("B" & fRowDataCalc & ":K" & lRowDataCalc).Copy .Range("B502")
               rowHght = .Range("B3").EntireRow.Height
               .Range("B501").RowHeight = rowHght
               lRowCopy = .Cells(Rows.Count, "C").End(xlUp).Row
               Set rng = .Range("B500:K" & lRowCopy)
           End With
   
           Set mySlide = myPresentation.Slides.AddSlide(myPresentation.Slides.Count + 1, PPLayout("LayoutEmittenten"))
           mySlide.Shapes.Placeholders(1).TextFrame.TextRange.Text = "Headline (" & i + 1 & ")"
           Call PasteEm(mySlide, rng)
           rng.Clear
       Next i
   
   End Sub
   
   Sub EmDataAn(wsEm As Worksheet, iSlides As Integer)
       Dim lRowAn As Long, fRowAn As Long, lRowData As Long, fRowDataCalc As Long, lRowDataCalc As Long
       Dim rng As Range
       Dim rowHght As Long, lRowCopy As Long
   
       lRowAn = wsEm.Cells(Rows.Count, 3).End(xlUp).Row
       fRowAn = wsEm.Cells(Rows.Count, 3).End(xlUp).End(xlUp).Row - 1
       lRowData = wsEm.Cells(Rows.Count, 10).End(xlUp).Row
   
       iSlides = iSlides + 1
       fRowDataCalc = 4 + 40 * iSlides + iSlides * 1
       lRowDataCalc = lRowData
   
       'Last sheet with data
       With wsEm
           .Range("B2:K3").Copy .Range("B500")
           .Range("B" & fRowDataCalc & ":K" & lRowDataCalc).Copy .Range("B502")
           rowHght = .Range("B3").EntireRow.Height
           .Range("B501").RowHeight = rowHght
           lRowCopy = .Cells(Rows.Count, "C").End(xlUp).Row
           Set rng = .Range("B500:K" & lRowCopy)
       End With
   
       Set mySlide = myPresentation.Slides.AddSlide(myPresentation.Slides.Count + 1, PPLayout("LayoutEmittenten"))
   
       mySlide.Shapes.Placeholders(1).TextFrame.TextRange.Text = "Headline (" & iSlides + 2 & ")"
       Call PasteEm(mySlide, rng)
       rng.Clear
       'Annotations
       Set rng = wsEm.Range("B" & fRowAn & ":K" & lRowAn)
       rng.Copy
       Set mySlide = myPresentation.Slides.AddSlide(myPresentation.Slides.Count + 1, PPLayout("LayoutEmittenten"))
       mySlide.Shapes.Placeholders(1).TextFrame.TextRange.Text = "Headline (" & iSlides + 2 & ")"
       Call PasteEm(mySlide, rng)
   End Sub
   
   
   
   Sub PasteEm(mySlide As PowerPoint.Slide, rng As Range)
       Dim myShape As PowerPoint.Shape
   
       rng.Copy
       DoEvents
       mySlide.Shapes.PasteSpecial DataType:=ppPasteEnhancedMetafile ' = 2
       Set myShape = mySlide.Shapes(mySlide.Shapes.Count)
       With myShape
           .Width = 683
           .Top = 70
           .Left = 5
       End With
   End Sub
   

这不是关于代码功能，而是如何使用变量。