web data connection

Column D is entering numeric data from a web connection (this data refreshes every 1 minute). In column H I want to paste all the data in column D and update this column every 24 hours to perform a percentage change calculation (in 24H%). At first it worked, but I realized that when the line goes up or down the column H stands still, it does not follow the data. This causes the data to not agree. I think of some function where if the line goes up or down, the data pasted in column H goes through this transition. Thanks!