How can events on user control trigger something on form?

I have been struggling with the following problem a bit: I have created a user control that contains a textbox and two labels. I have then added an ArrayList of these user controls to my windows form. I have also added a textbox (called txtTotal) to the windows form. This textbox (txtTotal) holds the total of all the values in the textboxes on the user controls. When the text changes event fires in the textbox on any of the user controls, I would like it to trigger an update of the total in txtTotal. I am a bit stuck with this problem at the moment. Can anyone give me some help? Thanks.