来个高手帮小弟我解决下VB的有关问题，多谢了

来个高手帮我解决下VB的问题，谢谢了！
Private   Sub   Form_Load()
        Dim   sBuffer   As   String
        Dim   lSize   As   Long
        sBuffer   =   Space$(255)
        lSize   =   Len(sBuffer)
        Call   GetUserName(sBuffer,   lSize)
        If   lSize   >   0   Then
                txtUserName.Text   =   Left$(sBuffer,   lSize)
        Else
                txtUserName.Text   =   vbNullString
        End   If
End   Sub


麻烦能给我解释下这是什么意思吗？
我在调试的时候总是在这里出问题！Thank   you!

[解决办法]
Public Declare Function GetUserName Lib "advapi32.dll " Alias "GetUserNameA " (ByVal lpBuffer As String, nSize As Long) As Long

[解决办法]
你需在窗体添加1文本框，名称改为txtUserName。此外下列API声明应放标准模块：
Public Declare Function GetUserName Lib "advapi32.dll " Alias "GetUserNameA " (ByVal lpBuffer As String, nSize As Long) As Long

[解决办法]
都==，让俺来解决