Creating and using private function in DLL

[muze]

hello guys... i am trying to make a dll in vc++. Now I need to use some private function in the dll so that they might do some work for other functions that are called by original application. Here is what I am trying to do

namespace MyDll
{
	class MyOwnDll
	{
	private:
		void msg();
	public:
		static _declspec(dllexport) double func(double a, double b);  
         }
}

namespace MyDll
{
         class MyOwnDll
         {

              void MyOwnDll::msg()
              { cout<<"The result is:  ";}

              void MyOwnDll::func(double a, double b)
               {   
                  msg(); //here is the error:'class::function' : illegal call of non-static member function
                  cout << a+b;       
               } 



         }
}

how can I accomplish this?? thnx