Excel forex formula help needed

[killerstein]

Soo, I have this worksheet as seen in the attached picture. Basically, I have this table with live exchange rates that refresh every minute. The exchange rate data is sourced from a website. The only relevant exchange rate from the table is the EUR/USD. On the left-hand side We have the current rate as well as the previous rates (although the last/most recent previous rate is the relevant one, which is the cell coloured in blue). On the bottom right, I have specified the rules that I want to have in my forex formula. I tried some things but because I am not very experienced with complex formulas, I couldn't manage to end up with a success. The initial transaction rate (left blank for now) is not very important. You can assume it as 1.215. In this case, we assume the role of an investor who has 1000 euros and (based on our assumed initial rate) he converts this into dollars at the 1.215 rate. This figure (1.215) is also our first Last Transaction Rate. Last Transaction Rate is the rate at which we last made a currency exchange. So, we have 1215 dollars in the beginning (or whatever dollars we have depending upon the initial rate we decide upon). Once the current, previous and last transaction rates fit the formula, we sell the dollars (at whatever the rate at the time) and our dollar account becomes 0 and our euro account now has the money. And then when we do the same thing with the euros (so when the rates are satisfactory and we sell the euros), the euro account will be emptied and now the dollar account will have the money. And during these transactions, the Last Transaction Rate will also be updated accordingly. Based on this information, what formulas do I need to enter in the cells under Account Balance (EUR), Account Balance (USD) and Last Transaction Rate (EUR/USD)?