如何在活动中创建一个柜台？

In Cell A1, I have formula that recalculates automatically every one to two seconds. When this cell recalculate, the old values from A1 is copied to cell B1. Every time it recalculates, I just want to get a running total. So far, what works is when there is a change in A1, the old value is copied to B1, but unable to get a running total every time it does this. The problem is In Cell A1, I have formula that recalculates au