VB编写播放器的代码问题

我用VB做一个播放器，但是只要一运行，mciGetErrorString函数得到到错误信息就会提示说“驱动程序不能识别指定命令的参数” 我检查了很多遍都没有找到错误所在
希望能有高手帮我看一下，小弟先谢了！

以下说程序段：

其中mediaFileName是一个已经声明的全局变量，lblFile是一个lable控件到名称，FileList是listbox控件的名称

Private Sub playMP3()
Dim str As String
Dim res As Long
Dim errorMsg As String * 500

str = "open " & mediaFileName & " alias mp3 type mpegvideo"
res = mciSendString(str, 0, 0, 0)
If res <> 0 Then
mciGetErrorString res, errorMsg, 500
MsgBox (errorMsg)
Exit Sub
End If

str = "play mp3 from 0"
res = mciSendString(str, 0, 0, 0)
If res <> 0 Then
mciGetErrorString res, errorMsg, 500
MsgBox (errorMsg)
Exit Sub
End If
End Sub

Private Sub lblFile_Click()

Dim strFile As String

CommonDialog1.D

mciSendString 的第二个参数是一个字符串

测试通过:

Option Explicit
Dim mediaFileName
Private Declare Function mciSendString Lib "winmm.dll" Alias "mciSendStringA" (ByVal lpstrCommand As String, ByVal lpstrReturnString As String, ByVal uReturnLength As Long, ByVal hwndCallback As Long) As Long
Private Declare Function mciGetErrorString Lib "winmm.dll" Alias "mciGetErrorStringA" (ByVal dwError As Long, ByVal lpstrBuffer As String, ByVal uLength As Long) As Long

Private Sub playMP3()
Dim str As String
Dim res As Long
Dim errorMsg As String * 500

str = "open " & mediaFileName & " type mpegvideo alias mp4 "
res = mciSendString(str, mediaFileName, 100, 0)
If res <> 0 Then
mciGetErrorString res, errorMsg, 500
MsgBox (errorMsg)
Exit Sub
End If

str = "play mp4"
res = mciSendString(str, 0&, 0, 0)