If you don't have the trade by trade P&L but equity (account balance), you can also use this method :
Assume equity is in A1:An. In column B, let B1 equal +A1. Then in B2 enter =IF(A2>=B1,A2,B1) and copy this down to Bn. In column C, let C1 equal +A1-B1 and copy this down to Cn. The maximum...