1. 可选参数Optional

Optional 代表本参数是可选项 =False ; 代表参数若不指定,则默认为False

Function mySumProduct(r As Range, Optional useColumn As Boolean = False)
End Function

Function mySumProduct(r As Range, Optional useColumn As Boolean = False)
    Dim i&, j&, s&, k&
    s = 0
    
    If useColumn Then
        
        For j = 1 To r.Columns.Count
            k = 1
            For i = 1 To r.Rows.Count
                k = k * r.Cells(i, j)
            Next i
           s = s + k
        Next i
       
    Else
        For i = 1 To r.Rows.Count
            k = 1
            For j = 1 To r.Columns.Count
                k = k + r.Cells(i, j)
            Next j
            s = s + k
        Next i
    
    
     mySumProduct = s
     
End Function

---

2.IsMissing判断参数是否提供,只能判断变体类型

3. 使用 := 可以按参数名传递参数 a:=1,c:=3

Sub callDemo()
    Dim x
    x = myFun(3)
    'x = myFun(3, 4)
    'x = myFun(3, 4, 5)
    'x = myFun(a:=3, c:=1)
    
End Sub

Function myFun(a, Optional b = 0, Optional c = 0)

    myFun = a + b - c
      
End Function

4.Msgbox 常用参数

Prompt: 第一参数,字符串
Buttons: 第二参数, Msgbox风格代码(可用常量名称,可用风格代码)
Title:第三参数, 对话框标题栏

. Msgbox的返回值代码

VBA_77">5.VBA颜色常量表