傳遞簡單變數 ByRef 和 ByVal

傳遞 ByRef 或 ByVal 表示引數的實際值是否通過 CallingProcedure 傳遞給 CalledProcedure，或者是否將參考（在某些其他語言中稱為指標）傳遞給 CalledProcedure。

如果引數傳遞給 ByRef，則引數的記憶體地址將傳遞給 CalledProcedure，並且 CalledProcedure 對該引數的任何修改都將轉換為 CallingProcedure 中的值。

如果引數傳遞給 ByVal，則實際值（而不是對變數的引用）將傳遞給 CalledProcedure。

一個簡單的例子將清楚說明這一點：

Sub CalledProcedure(ByRef X As Long, ByVal Y As Long)
    X = 321
    Y = 654
End Sub

Sub CallingProcedure()
    Dim A As Long
    Dim B As Long
    A = 123
    B = 456

    Debug.Print "BEFORE CALL => A: " & CStr(A), "B: " & CStr(B)
    ''Result : BEFORE CALL => A: 123 B: 456

    CalledProcedure X:=A, Y:=B

    Debug.Print "AFTER CALL =  A: " & CStr(A), "B: " & CStr(B)
    ''Result : AFTER CALL => A: 321 B: 456
End Sub

另一個例子：

Sub Main()
    Dim IntVarByVal As Integer
    Dim IntVarByRef As Integer
    
    IntVarByVal = 5
    IntVarByRef = 10
    
    SubChangeArguments IntVarByVal, IntVarByRef '5 goes in as a "copy". 10 goes in as a reference
    Debug.Print "IntVarByVal: " & IntVarByVal 'prints 5 (no change made by SubChangeArguments)
    Debug.Print "IntVarByRef: " & IntVarByRef 'prints 99 (the variable was changed in SubChangeArguments)
End Sub

Sub SubChangeArguments(ByVal ParameterByVal As Integer, ByRef ParameterByRef As Integer)
    ParameterByVal = ParameterByVal + 2 ' 5 + 2 = 7 (changed only inside this Sub)
    ParameterByRef = ParameterByRef + 89 ' 10 + 89 = 99 (changes the IntVarByRef itself - in the Main Sub)
End Sub