How to send a command between views?

I have an app that has a view (lets call it BlueView) that has various buttons on it that when pressed load a modal view that lets you select a date (lets call this view DatePick). I figured out how to pass the date back to the BlueView. The date that was picked will be used in a sub that exists in BlueView called calculate. What I need to figure out now is how do I call the calculate sub from the DatePick view as it is being dismissed? I don't know if i explained this good enough, and I've researched this as best I can. I simply don't know what the command/code that would invoke this is called. I am fairly new to this, but I have been able to work through numerous obstacles so far in my app design. I'm not looking for someone to post code that I can cut and paste, I just need to be lead in the right direction. Any help would be greatly appreciated. Thanks.

 

Ok, I've been trying to figure this out and I am missing something. I set up the Protocol in BlueViewController.h like so;

@protocol dateset
[self performSelectorselector(calculate)];
@end

I added #include "BlueViewController.h" to DatePickController.m and in the selectButtonPressed method I put

@protocol (dateset);

The date definitely gets passed to the BlueView when I press the Select button, but I can't call the calculate method in BlueViewController.m. I know something with the syntax for the protocol is incorrect, but I can't figure out what. I probably didn't describe this perfectly, but by the other posts I hope you can figure out what I am doing. Thanks for helping a newbie.