How to develop accumulator codes?

Hi everyone! This is for vb.net which I've been working to develop a system which involves computation. I would just like to ask for any ideas or source code or a link perhaps that could help me resolve this issue. What I've been trying to develop in my program is, I have a textbox where user will enter a numeric value,there is a button and a label below and in the first place the label should be set to zero.Everytime you enter a numeric value in the textbox and click the button it should add the value in the label and should save the value in the label so even if you exit the program whatever the last value displayed in the label should remain the same when run the program again,I believe it requires a database to save the value. Basically its like with payment system which saves the total amount of all payments made. This is how should it works,say for example,if you will enter 1,2,3 it should save the sum value which is 6 in the label even if you close the program and when you run it again and enter another value it should add to the current value which is 6. I would greatly appreciate for any informative response.