Global variables and global fields will work equally well for this in most situations.
You might also investigate the New Window command. There are ways to use New Window to pop up a small "pseudo-modal" window that displays content from one of your layouts--this enables check boxes, radio buttons, conditional formatting, etc. which can't be done with Show Custom Dialog.
Thanks for the suggestion Phil
I plan to setup a Dialog Type in my message table I could use this to handle the "Window" ones too though at the moment Im not sure what Id use it for.
Im having so much fun building up my environment with toys I need to get down to actually building my app.
. . . . as well as value lists, which I consider the biggest reason to use "New Window" over Custom Dialog.