Need code for multiple VB2005 applications to communicate with each other

I am looking for an example of code to be used with Visual Basic 2005 to enable separate applications to easily communicate with each other to pass information to each other. Example: Program1 looks to see if Program2 is running, if true then Program1's String1 = Program2's String1. It would also be helpful to essentially bind the variables in each program so that when Program1's String1 changes then Program2's String1 automatically changes and vice versa. I don't need to keep any information after programs are closed, they only need to communicate or sync together while open. I will have lots of variables in many programs changing very fast so the method needs to be efficient. Maybe the variables can be declared somehow to a system level and not restrained to the particular application so any application can access them? How you solve it isn't important, as long as it's not too complicated so I can easily add it to my Visual Basic 2005 programs. I only need an example of how this can work between two programs and two variables, once I know that much I can expand it myself. I think this should be very simply for an experienced programmer, I just have no idea how to do this. Thank you!