Private Sub Command1_Click()
Dim a(1 To 4, 1 To 13)
n = 0
For Each i In a
n = n + 1
Next
MsgBox "数组a包含的元素的个数为 " & n
Dim b(5 To 5, 1 To 2)
n = 0
For Each i In b
n = n + 1
Next
MsgBox "数组b包含的元素的个数为 " & n
End Sub

我对此了解不深，粗略解释。
语句只为集合与数组二种数据类型专门度身定做的
For Each <成员> In <数组或集>
[遍历个成员]
Next [<成员>]
数组例不用举了，下面为一集合例子
Private Sub Form_Click()
Dim objCtrl As Object
For Each objCtrl In Me.Controls
Print objCtrl.Name
If Left$(objCtrl.Name, 3) = "Pic" Then
Print " Left=" & CStr(objCtrl.Left)
End If
Next
End Sub