I have the need to programmatically RDP to a virtual machine(XP SP3 / .NET3.5 / VS 2008), (credentials have been saved in .rdp file) and do UI automation testing. Because of our domain security, I need to programmatically answer 'ok' to the interactive logon. I am able to access other dialogue Windows and SendMessages to buttons, etc, after login, but I have not been able to get my SendMessage to work on this initial screen. I used spy++ to capture what actually gets sent when I press enter and I seem to be able to duplicate those messages as I view the response in the spy++ log as I run my program, but no matter what variant I use in the message nothing happens.
I would like to know if it is even possible to programmatically do this or does the OS prevent this kind of automation due to security issues?

The messages I see in spy++ when I hit the enter button( on that initial screen it seems any key will do) I see:

WM_KEYDOWN nVirtKey:00FF cRepeat:1 ScanCode:00 fExtended:0 fAltDown:0 fRepeat:0 Up:0
WM_KEYUP nVirtKey:00FF cRepeat:1 ScanCode:00 fExtended:0 fAltDown:0 fRepeat:1 Up:1

When I exercise the code below and watch the messages sent to IHWindowClass(hwnd6 below) I see I generate the above messages to that window. Any help would be appreciated!

Here are the pertinent sections of the code:

UIntPtr ip = new UIntPtr(0x0D); //ENTER
UIntPtr ip2 = new UIntPtr(0xFF); //00FF
UIntPtr kyDwnlParam = new UIntPtr(0x001);
UIntPtr kyUplParam = new UIntPtr(0xc0000001);

// used UISpy to get these class names...
string lpszParentClass = "TscShellContainerClass";
string lpszParentWindow = "test2 - test2 - Remote Desktop Connection";
string lpszClass2 = "TscShellAxHostClass";
string lpszClass3 = "ATL:2D33D580";
string lpszClass4 = "UIMainClass";
string lpszClass5 = "UIContainerClass";
string lpszClass6 = "IHWindowClass";

hWnd2 = FindWindowEx(ParenthWnd, IntPtr.Zero, lpszClass2, IntPtr.Zero);
hWnd3 = FindWindowEx(hWnd2, IntPtr.Zero, lpszClass3, IntPtr.Zero);
hWnd4 = FindWindowEx(hWnd3, IntPtr.Zero, lpszClass4, IntPtr.Zero);
hWnd5 = FindWindowEx(hWnd4, IntPtr.Zero, lpszClass5, IntPtr.Zero);
hWnd6 = FindWindowEx(hWnd5, IntPtr.Zero, lpszClass6, IntPtr.Zero);

string hexValue = hWnd6.ToString("X"); //Convert to hex to use find in spy++

SetForegroundWindow(hWnd6); // for good measure....

// tried this....

SendMessage(hWnd6, (uint)WindowsUtilities.WindowsMessages.WM_KEYDOWN, ip2, kyDwnlParam);
SendMessage(hWnd6, (uint)WindowsUtilities.WindowsMessages.WM_KEYUP, ip2, kyUplParam);

// tried this....
SendMessage(hWnd6, (uint)WindowsUtilities.WindowsMessages.WM_KEYDOWN, ip, kyDwnlParam);
SendMessage(hWnd6, (uint)WindowsUtilities.WindowsMessages.WM_KEYUP, ip, kyUplParam);

// tried this...
SendMessage(hWnd6, (uint)WindowsUtilities.WindowsMessages.WM_CHAR, ip, UIntPtr.Zero);
SendMessage(hWnd6, (uint)WindowsUtilities.WindowsMessages.WM_CHAR, ip, UIntPtr.Zero);