Forms :: Custom Dialogue Box In Vb 2008?

I would like to generate some custom dialog boxes that I can call from anywhere in my project.

The easiest example I can give is of a form that waits for two numbers to be entered then returns their sum. I want to call it like a function ie. sum = add_two_numbers( " Enter the numbers you want to add then click add)This is not what I actually want to do, that is far more complex, this just a simple way to explain what I want to do. If I can do this I can do what I really want.

Essentially I want forms that will accept some input, process it and return a string. A bit like an input inputbox, an openfiledialog box or a fontdialog box. I also need to pass strings to it.I can do it if I use a function declared in a module which calls the form and then returns the value once it is calculated but isn't there a simpler more elegant method?