loop in a button

[var5an1]

code:

tried for and do whil loop..

the amount is already set to 1.00

every time the user clicks on the "10p" button it deducts 10p

until it gets to 0 if its more then 0 its give change

if (e.getActionCommand().equals("10p"))
{
..can u help me what code goes here inc calculation
}

thank u

[var5an1]

need help for the amount to decrement when a button is pressed