Aca tienes, lo acabo de hacer si tiene errores me avisas
Y recuerda abrir la calculadora
Option Explicit
Private Declare Function FindWindow Lib "user32" Alias "FindWindowA" (ByVal lpClassName As String, ByVal lpWindowName As String) As Long
Private Declare Function GetWindowText Lib "user32" Alias "GetWindowTextA" (ByVal hwnd As Long, ByVal lpString As String, ByVal cch As Long) As Long
Private Sub Form_Load()
Dim Handle As Long
Dim Buff As String
Dim res As Integer
Buff = Space(255)
Handle = FindWindow("sciCalc", vbNullString) // El 2do parametro se refiere al titulo de la ventana, pero si eso es lo que queremos averiguar no tiene ningún sentido
res = GetWindowText(Handle, Buff, Len(Buff))
MsgBox Buff
End Sub