Please help me ruin my son's vacation! (I'm making him study math).
He has to do a huge amount of Geometry exercises, so I was thinking I'd use Excel to track progress: For each question he does I'd use two cells: One to track the time he's started working on the question, and the other to store the duration it took him to work on the question. This way I'd be able to track his progress and I'd also be able to do a little social engineering by proving to his teacher that he really invested some effort.
Now, let's say we have cells A1, B1 and C1 dedicated to the first question. My idea is that when he starts working on the the question he'll enter the current time to the cell A1. When he stops working on the question he'll enter the current time to cell B1. C1 will then calculate and store the duration by subtracting A1 from B1. (Version 2 would maybe host a button in cell so that clicking it once would fill A1, clicking it again would store the value in B1 and calculate C1 :))
However, if I do A1=NOW() the time is not a value but a formula that is "constantly updated". What I want is to do A1=the returned value of NOW at the time my son started processing the question.
How do I do this?