First off, you only have the handle of the Edit window which is the textbox you enter "/status". You need the handle of the window that has the information in it. Since I don't have this program I am not sure what type of control it is. But you would find it the same way you found the edit textbox.
After you find it, you can use the code you had before...
Dim txtLength As Long = SendMessage(x, WM_GETTEXTLENGTH, CInt(0), CInt(0)) + 1
Dim txtBuff As String = Space(txtLength)
Dim TEMP As Long = TEMP = SendMessage(x, WM_GETTEXT, txtLength, txtBuff)
MessageBox.show(txtBuff)
The only problem with the code you currently have is that x is the handle of the (aforementioned) Edit control that corresponds to the input textbox. So find the handle of the other control and use that as the hWnd arguement.