how to get the value of a text box???

There are some declarations and code that you can erase to make it shorter.

Private Declare Function FindWindowEx Lib "user32" Alias "FindWindowExA" (ByVal hWnd1 As Long, ByVal hWnd2 As Long, ByVal lpsz1 As String, ByVal lpsz2 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 hResult
    hResult = FindWindowEx(FindWindowEx(0, 0, "SciCalc", vbNullString), 0&, "Static", vbNullString)
    Debug.Print GetWndText(hResult)
End Sub

Private Function GetWndText(ByVal hwnd As Long)
    Dim temp As String * 255
    GetWindowText hwnd, temp, 255
    GetWndText = Left(temp, Len(temp) - InStr(1, temp, vbNullChar))
End Function