I had to create a Totally new DLL like thise and Reference that dll into my Own Code.
This call contains only two methods one to CallFunctionforManagedDLL and CallFunctionForUnmanagedDLL
public class DLL : MarshalByRefObject
{

}

2) In my own Code now i have to first check whether the dll user has given as path is Managed or Unmanaged

using (FileStream fs = File.Open(tbDLLPath.Text, FileMode.Open))
{
using (MemoryStream ms = new MemoryStream())
{
byte[] buffer = new byte[1024];
int read = 0;
while ((read = fs.Read(buffer, 0, 1024)) > 0)
ms.Write(buffer, 0, read);
Assembly assembly = Assembly.Load(ms.ToArray());
}
}

Above code will help you to find that. If Assembly.Load throws an exception that means
It is Unmanaged DLL.

3) Now Create a totally New Appdomain

AppDomain Temporary = AppDomain.CreateDomain("Temporary");
try
{
//Creates new Type in Temp Domain
DLL Proxy = (DLL)Temporary.CreateInstanceAndUnwrap("DLLAppDoma in", "DLLAppDomain.DLL");



if (managed)
{
MessageBox.Show("Executing Managed DLL");
Object retobj = Proxy.CallManagedDLLFunction(dllFilePath, methodeName, arg, types);

}
else
{
MessageBox.Show("Executing Unmanaged DLL");
Object retobj = Proxy.CallUnmanagedDLLFunction(dllFilePath, methodeName, arg, types,returnType, UnloadDll);

}


4) In the CallUnamagedDLLFunction..one thing you should make sure that you unload the DLL file from the module. after you have executed the Function Dynamically.

// For HtmlHelpA function the code was acting weird
// When i execute the code the Help file is opened but after that the
// MyApplication crashes..If i go in debug mode and close the help file after it is opened
// everything seems to work. New idead to put CheckBox that will ask user


// if they want to Free or Unload a DLL after its execution is done.
if (UnloadDLL)
{
IntPtr ptr = GetModuleHandle(filename);
FreeLibrary(ptr);
}

This will help you unlock the DLL file your application was using during execution.

5) Finally Unload the Appdomain..
finally
{
AppDomain.Unload(Temporary);
}