how to set a row's value from a certain row's value?

Question

I have a MySQL table named "activities" with fields id(int), tstamp(timestamp), amount(decimal) balance(decimal). Decimal fields hold money values.

id   tstamp                   amount   balance
----------------------------------------------
 1   2013-03-18 00:00:10       57.00      0.00
 2   2013-03-18 00:00:11       13.05      0.00
 3   2013-03-18 00:00:12      110.00      0.00
 4   2013-03-18 00:00:13       23.50      0.00
 5   2013-03-18 00:00:14       35.44      0.00
 6   2013-03-18 00:00:15       76.00      0.00
 7   2013-03-18 00:00:16       34.74      0.00
 8   2013-03-18 00:00:17      120.47      0.00
 9   2013-03-18 00:00:18       35.00      0.00
10   2013-03-18 00:00:09       46.00      0.00

so balance fields' values must be like that: current row's balance = CHRONOLOGICALLY previous row's balance + current row's amount.

Notice last row's tstamp value is smaller than first row's tstamp value. so when I say previous row I do not mean current id minus 1. So highest balance value must be at row #9.

And the problem is how to update all balances with chronogically previous row's balance value + current row's amount value?