Forms :: Bank User Form - Recording Deposits And Withdrawals

I want to create a form where i can be recording the deposits and withdrawals of my bank account!

Let's say I don't have any deposit. If I want to add then i would click on the "+Deposit money" button to open a form to add let's say 10$.

so my total would be 10$.

Next record would to add 30$

so my new total would be 40$ (10$ + 30$)

NOW if i make a withdrawal from my account i would like to click on the "- withdraw money" and so my total would change!

so if i withdraw 5$ the new total would be

35$ (total 40$ - 5$)

how can i do that?!!!