Backtest using BuyPrice and SellPrice when signal arrives

When I backtest the options of buyPrice and SellPrice are limited to only OHLC or Average, but I want it to show the buyprice as the price at which the signal arrived. How to do that? @Tomasz

Assign BuyPrice yourself in the formula, http://www.amibroker.com/guide/h_backtest.html and http://www.amibroker.com/kb/2014/11/26/handling-limit-orders-in-the-backtester/

This brings out one more question:
How to set buyprice= the exact price when a buy signal comes.
for example:
buy = close > 245;
so how to set buyprice = 245.05 or something like that.