Time stamp in a live streaming excel sheet (Stock Market)

Let us say I have Columns A to G in the excel sheet and the columns heading reading as below for stock market : Symbol, Lot Size, Open, High, Low, LTP and the Signal Column (which gives Buy or Sell based on a strategy). The last column which is the Signal Column (and which happens to be Column G) contains the “Buy”or “Sell” or Ëmpty when there is no signal. This column is dynamic, in the sense, as and when the data across A-F changes, I get new signals like Buy or Sell or Empty, depending upon the strategy. My expectation is, as and when I get a Buy or a Sell or an empty in Column G (in the event of a Buy and Sell that has changed to an empty cell), I want to timestamp, let us say, Column H with the exact time the change happened (regardless of Buy or Sell or empty (post a buy or sell). And this timestamp should not change the time, unless any change happens in Column G. For e.g. a buy changing to a sell or a sell changing to a buy or a buy/sell changing to an empty cell. The challenge I have with the available solution on the net is, my Excel sheet refreshes every 1 minute pulling data off the net, and as and when it does, the timestamp changes to the current time as against the time the signal came. For e.g. a BUY or SELL that came at say 11:15 AM, should remain static unless the signal changes from a buy to sell or a sell to buy, but everytime my excel refreshes it updates with the current time in this column. What I am looking for is to understand what time a buy or sell came Data Sheet snapshot : My excel sheet, where Column F contains live signals (Buy or Sell) and Column T should contain the Trigger time (timestamp) as and when there is a change in Column F Jackpot : The sheet snapshot that was available on the internet, and which is precisely I want in my excel sheet.