Private Declare Function SendMessage Lib "user32" _
  Alias "SendMessageA" ( _
  ByVal hWnd As Long, _
  ByVal wMsg As Long, _
  ByVal wParam As Long, _
  lParam As Any) As Long
 
Private Const EM_GETLINE = &HC4
Private Const EM_GETSEL = &HB0
Private Const EM_LINEFROMCHAR = &HC9
Private Const EM_LINEINDEX = &HBB
Private Const EM_LINELENGTH = &HC1
 
Private Function GetSelText(oTextBox As TextBox, Optional ByVal nLine As Long = _
  0) As String
 
    Dim CursorPos As Long
    Dim FirstChar As Long
    Dim RowLength As Long
    Dim Buffer() As Byte
 
 
        ' Falls keine Zeilennummer angegeben, Inhalt der aktuellen Zeile 
        ' ermitteln
        If nLine < 1 Then
          CursorPos = SendMessage(oTextBox.hWnd, EM_GETSEL, 0, ByVal 0&) \ 65536
          nLine = SendMessage(oTextBox.hWnd, EM_LINEFROMCHAR, CursorPos, ByVal _
            0&)
        Else
          nLine = nLine - 1
        End If
 
        ' Zeilenlänge ermitteln
        FirstChar = SendMessage(oTextBox.hWnd, EM_LINEINDEX, nLine, ByVal 0&) + _
          1
        RowLength = SendMessage(oTextBox.hWnd, EM_LINELENGTH, FirstChar, ByVal _
        0&)
 
        Dim lngPos As Long
            lngPos = InStr(1, Mid(oTextBox.Text, FirstChar, RowLength), " ")
 
        If lngPos > 0 Then GetSelText = Mid(oTextBox.Text, FirstChar, lngPos - 1)
 
End Function
 
Private Sub Command1_Click()
    MsgBox """" & GetSelText(Text1) & """"
End Sub

Mit freundlichen Gr??en,
Andy G.