Updating ListBoxes and RichTextBoxes when a variable is changed

Question

Hi everyone,

Im currently trying to get a hold on programming windows forms using c# and im having trouble doing alot of the simple stuff i want to do, one of things i want to get going is updating the contents of a textbox with the values of a variable everytime the change say i change a string variable i want the change to be reflected in a textbox on another form automatically also where do i put variable to be used on multiple forms

cheers

-Tristan