Communication between instances

Hi,

I've been trying to get 2 instances to communicate with each other, like calling each other functions but I cannot create a new object as I would lose information and privileges. It is some thing similar to web services on the same machine, any ideas on how to do it?
is it possible to grab a handle to an instance using GUID and using it's functions?

Thanks
Gdisia

2 instances of what? EXEs? Classes?

If this is between two exes on same machine then create two files and let each be polling to read / write them

Applications like Word or Excel are usable from within your programs if they're running because they register themselves with the Windows ROT. (Can't remember what it stands for though...) If you can register your EXE with the ROT, other programs can create objects out of it. Search the net for how to do this, I've seen it somewhere, although it's probably highly technical.
The other option is to use an ActiveX EXE client/server model to allow communication, but it really depends on how much coding you want to do. Allowing them both to read and write a file (as mentioned above) is perfectly acceptable in some circumstances.