Textbox Counter

Hi, I am trying to figure out a simple counter for a textbox, but cannot seem to get it to work. I have a userform with a textbox that is used for counting jobs. I want to enter a quantity in the textbox, press the commandbutton, store the number entered (lets say 3). Now when I start the next job, enter a number in the quantity box (4), press the button and now need to update the total box to 7 ... and so on. What I have just appends the textbox, so these qtys show up as "34"

Thanks for any help...