User defined call back functions as parameter in ALT COM dll

I have created a c++ console application. Now I want to build a ALT COM object so that I can use the C++ code in other platforms(eg. C#). One of the functions RegisterListener(parameter1, parameter2) takes two call back (out) functions as parameters. I have seen videos/documentations but all of them build COM dll where parameters are built in data types(int, long, bool, HRESULT, etc). How can I use user defined callback(out) functions as parameter.
Example:

sigin(int,string);
signout(string);
RegisterListener( (sigin)(int,string), signout(string) );

I want to allow the function RegisterListener to be called by other programs using the COM dll How can I do this/Are there any tutorials regarding this? Note: I have never wrote any COM objectsdll before.