百思不得其解？？（这个程序是获取某磁盘是否存在，存在则写入文件）
我定义了m ,怎么还提示变量未定义啊。请高手帮忙，帮我修改下出了什么问题。
代码如下：
Private Declare Function GetDriveType Lib "kernel32" Alias "GetDriveTypeA" (ByVal nDrive As String) As Long
Dim a As Long

Private Sub Timer1_Timer()
Dim m As String
Dim i As Long

m = CDEFGHIJKLMNOPQRSTUVWXYZ

For i = 1 To 23
a = GetDriveType(Left(m, i) & ":")
If a = 3 Then
Open App.Path & "\Log.txt" For Append As #1
Print #1, Left(m, i) & "盘存在"
Close #1
End If
i = i + 1
Next

End Sub

[解决办法]
m = "CDEFGHIJKLMNOPQRSTUVWXYZ"
[解决办法]
i=i+1　这句多余
[解决办法]
应该用（Mid(m, i, 1) & ":"）