I am trying to determine the state of a checkbox in an external program from a VB.Net WinForm application. I used Spy++ to get the handle of the checkbox. I convert the handle from hex to decimal, and enter it into a textbox (I automatically extract the handle in my full application). I can toggle the checkbox from my program, so I know i have the correct handle. However I can not seem to GETSTATE or GETCHECK using SendMessage. I was not sure which I should be using, but they both always return 0. Here is my module code:


Code:
Imports System.Runtime.InteropServices
Module Module1

    Public Const BM_CLICK = &HF5
    Public Const BM_GETCHECK = &HF0
    Public Const BM_GETSTATE = &HF2

    <DllImport("user32.dll", SetLastError:=True, CharSet:=CharSet.Auto)> Private Function SendMessage(ByVal hWnd As IntPtr, ByVal Msg As UInteger, ByVal wParam As Integer, ByVal lParam As Integer) As Integer
    End Function

    Sub toggle(hwnd As IntPtr)
        SendMessage(hwnd, BM_CLICK, 0, 0)
    End Sub

    Function GetCheck(hwnd As IntPtr) As Integer
        Return SendMessage(hwnd, BM_GETCHECK, 0, 0)
    End Function

    Function GetState(hwnd As IntPtr) As Integer
        Return SendMessage(hwnd, BM_GETSTATE, 0, 0)
    End Function
End Module
and my form code

Code:
Public Class Form1
    Private Sub btnToggle_Click(sender As Object, e As EventArgs) Handles btnToggle.Click
        Dim hwnd As IntPtr = CType(TextBox1.Text, IntPtr)
        toggle(hwnd)
    End Sub

    Private Sub btnGetStatus_Click(sender As Object, e As EventArgs) Handles btnGetStatus.Click
        Dim hwnd As IntPtr = CType(TextBox1.Text, IntPtr)
        lblState.Text = GetState(hwnd).ToString
    End Sub

    Private Sub btnGetChk_Click(sender As Object, e As EventArgs) Handles btnGetChk.Click
        Dim hwnd As IntPtr = CType(TextBox1.Text, IntPtr)
        lblCheck.Text = GetCheck(hwnd).ToString
    End Sub
End Class
Any help would be appreciated