'窗体申明部分
Private Declare Function GetUserName Lib "advapi32.dll" Alias "GetUserNameA" (ByVal lpbuffer As String, nSize As Long) As Long
'具体实现部分
Private Sub Form_Load()
On Error Resume Next
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