How do I call CreateProcessAsUser from Visual C#?

I am writing a scheduling service to replace one written in Delphi.  Here, I need to create a process from the service application which will be invoked by a specified user on that user's desktop.  Otherwise, they cannot see the application they have scheduled running and become especially ill tempered.  (They are always testy...)

I found lovely code on Microsoft.com (http://support.microsoft.com/kb/q165194/) to do this, but it is written in C++, a language which I am loth to use for this purpose.

I do well until I run into code which uses heap_alloc() getting the logon sid of the user.  I have no signature for the TOKEN_GROUPS struct.   I have attempted to define it and plug it into the code, but I keep getting problems with C# seeing my struct as managed code.

The attached snippet holds both my definitions and the code to the point from which I am not able to proceed.

I know this is nasty, but I would appreciate even the smallest of hints...

Digga

[DllImport("kernel32.dll", SetLastError = true)]
        static extern IntPtr HeapAlloc(IntPtr hHeap, uint dwFlags, UIntPtr dwBytes);
 
...
 
   unsafe  public struct SID_AND_ATTRIBUTES
        {
          public  IntPtr Sid;
           public  UInt32 Attributes;
        }
    unsafe public struct TOKEN_GROUPS
        {
           public UInt32 GroupCount;
           public  SID_AND_ATTRIBUTES[] Groups;
 
...
 
 
      bool ObtainSid(IntPtr hToken, IntPtr psid)
            
        {
            bool bSuccess = false;
            IntPtr ptg = IntPtr.Zero;
             UInt32 dwIndex = 0;
             uint dwLength = 0;
             TOKEN_INFORMATION_CLASS tic = TOKEN_INFORMATION_CLASS.TokenGroups;
            
            try
            {
                if (!GetTokenInformation(hToken, tic, ptg, 0, out  dwLength))
                {
                    if (Marshal.GetLastWin32Error() == ERROR_INSUFFICIENT_BUFFER)
                    {
 
                        ptg = HeapAlloc(GetProcessHeap(),HEAP_ZERO_MEMORY,dwLength);
 
                        // more to come, if I can get the above to compile and work,
 
                    }
                }
 
                
         
                bSuccess = true;
            Leave: ;
            }
            finally
            {
 
 
            }
            return bSuccess;
        }
 
 
Error	1	The best overloaded method match for 'SchedulerIIProofOfConcept.Form1.HeapAlloc(System.IntPtr, uint, System.UIntPtr)' has some invalid arguments	C:\Documents and Settings\jjalbert\Desktop\Scheduler 2\SchedulerIIProofOfConcept\Form1.cs	422	31	SchedulerIIProofOfConcept

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